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1
Kaiser, P. E., J. A. Seawright und B. K. Birky. „Chromosome polymorphism in natural populations of Anopheles quadrimaculatus Say species A and B“. Genome 30, Nr. 2 (01.04.1988): 138–46. http://dx.doi.org/10.1139/g88-024.
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Ovarian polytene chromosomes from eight populations of Anopheles quadrimaculatus in the southeastern United States were observed for chromosomal polymorphisms. Two sibling species, species A and B, each with intraspecific inversions, were distinguished. Species A correlates with the previously published standard maps for salivary gland and ovarian nurse-cell polytene chromosomes. Species A was found at all eight collection sites, and five of these populations also contained species B. Three inversions on the right arm of chromosome 3 were observed in species A. Species B contained a fixed inversion on the X chromosome, one fixed and one floating inversion on the left arm of chromosome 2, and one fixed and one floating inversion on the right arm of chromosome 3. The fixed inversion on the X chromosome makes this the best diagnostic chromosome for distinguishing species A and B. An unusual dimorphism in the left arm of chromosome 3, found in both species A and B, contained two inversions. The heterokaryotypes, as well as two distinct homokaryotypes, were seen in all of the field populations. Intraspecific clinal variations in the frequencies of the species A inversions were noted. The Florida populations were practically devoid of inversions, the Georgia and Alabama populations contained some inversions, and the Arkansas population was mostly homozygous for two of the inversions. The phylogenetic relationships of species A and B to the Maculipennis complex (Nearctic) are discussed.Key words: Anopheles, inversion, populations, chromosome polymorphism, phylogenetics.
2
Ruiz, Alfredo, José María Ranz, Mario Cáceres und Carmen Segarra. „Chromosomal evolution and comparative gene mapping in the Drosophila repleta species group“. Brazilian Journal of Genetics 20, Nr. 4 (Dezember 1997): 553–65. http://dx.doi.org/10.1590/s0100-84551997000400003.
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A review of our recent work on the cromosomal evolution of the Drosophila repleta species group is presented. Most studies have focused on the buzzatii species complex, a monophyletic set of 12 species which inhabit the deserts of South America and the West Indies. A statistical analysis of the length and breakpoint distribution of the 86 paracentric inversions observed in this complex has shown that inversion length is a selected trait. Rare inversions are usually small while evolutionary successful inversions, fixed and polymorphic, are predominantly of medium size. There is also a negative correlation between length and number of inversions per species. Finally, the distribution of inversion breakpoints along chromosome 2 is non-random, with chromosomal regions which accumulate up to 8 breakpoints (putative "hot spots"). Comparative gene mapping has also been used to investigate the molecular organization and evolution of chromosomes. Using in situ hybridization, 26 genes have been precisely located on the salivary gland chromosomes of D. repleta and D. buzzatii; another nine have been tentatively identified. The results are fully consistent with the currently accepted chromosomal homologies between D. repleta and D. melanogaster, and no evidence for reciprocal translocations or pericentric inversions has been found. The comparison of the gene map of D. repleta chromosome 2 with that of the homologous chromosome 3R of D. melanogaster shows an extensive reorganization via paracentric inversions and allows to estimate an evolution rate of ~1 inversion fixed per million years for this chromosome
3
Fuller, Zachary L., Spencer A. Koury, Christopher J. Leonard, Randee E. Young, Kobe Ikegami, Jonathan Westlake, Stephen Richards, Stephen W. Schaeffer und Nitin Phadnis. „Extensive Recombination Suppression and Epistatic Selection Causes Chromosome-Wide Differentiation of a Selfish Sex Chromosome in Drosophila pseudoobscura“. Genetics 216, Nr. 1 (30.07.2020): 205–26. http://dx.doi.org/10.1534/genetics.120.303460.
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Sex-Ratio (SR) chromosomes are selfish X-chromosomes that distort Mendelian segregation and are commonly associated with inversions. These chromosomal rearrangements suppress recombination with Standard (ST) X-chromosomes and are hypothesized to maintain multiple alleles important for distortion in a single large haplotype. Here, we conduct a multifaceted study of the multiply inverted Drosophila pseudoobscura SR chromosome to understand the evolutionary history, genetic architecture, and present-day dynamics that shape this enigmatic selfish chromosome. The D. pseudoobscura SR chromosome has three nonoverlapping inversions of the right arm of the metacentric X-chromosome: basal, medial, and terminal. We find that 23 of 29 Mb of the D. pseudoobscuraX-chromosome right arm is highly differentiated between the Standard and SR arrangements, including a 6.6 Mb collinear region between the medial and terminal inversions. Although crossing-over is heavily suppressed on this chromosome arm, we discover it is not completely eliminated, with measured rates indicating recombination suppression alone cannot explain patterns of differentiation or the near-perfect association of the three SR chromosome inversions in nature. We then demonstrate the ancient basal and medial inversions of the SR chromosome contain genes sufficient to cause weak distortion. In contrast, the younger terminal inversion cannot distort by itself, but contains at least one modifier gene necessary for full manifestation of strong sex chromosome distortion. By parameterizing population genetic models for chromosome-wide linkage disequilibrium with our experimental results, we infer that strong selection acts to maintain the near-perfect association of SR chromosome inversions in present-day populations. Based on comparative genomic analyses, direct recombination experiments, segregation distortion assays, and population genetic modeling, we conclude the combined action of suppressed recombination and strong, ongoing, epistatic selection shape the D. pseudoobscura SR arrangement into a highly differentiated chromosome.
4
Ramírez, Corália CL, und Eliana MB Dessen. „Chromosomal evidence for sibling species of the malaria vector Anopheles cruzii“. Genome 43, Nr. 1 (01.02.2000): 143–51. http://dx.doi.org/10.1139/g99-103.
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An analysis of the ovarian polytene chromosomes of Anopheles cruzii from three localities in Southeast Brazil revealed the existence of two genetic entities within this morphologically uniform taxon. These cryptic species differed in the banding patterns of the X chromosome and 3L arm. A pattern of bands that cannot be explained by the fixation of any of the known inversions in chromosome X was revealed and named chromosomal form B to distinguish it from the standard pattern of this X chromosome, form A. Each chromosomal form is characterized by a different set of inversions. The lack of heterozygotes (A/B) for these X chromosome forms in populations where both forms coexist is evidence of absence or limited gene flow between the two groups. Key words: Anopheles cruzii, inversion polymorphism, sibling species.
5
Eggleston, William B., Nac R. Rim und Johng K. Lim. „Molecular Characterization of hobo-Mediated Inversions in Drosophila melanogaster“. Genetics 144, Nr. 2 (01.10.1996): 647–56. http://dx.doi.org/10.1093/genetics/144.2.647.
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Abstract The structure of chromosomal inversions mediated by hobo transposable elements in the Uc-1 X chromosome was investigated using cytogenetic and molecular methods. Uc-1 contains a phenotypically silent hobo element inserted in an intron of the Notch locus. Cytological screening identified six independent Notch mutations resulting from chromosomal inversions with one breakpoint at cytological position 3C7, the location of Notch. In situ hybridization to salivary gland polytene chromosomes determined that both ends of each inversion contained hobo and Notch sequences. Southern blot analyses showed that both breakpoints in each inversion had hobo-Notch junction fragments indistinguishable in structure from those present in the Uc-1 X chromosome prior to the rearrangements. Polymerase chain reaction amplification of the 12 hobo-Notch junction fragments in the six inversions, followed by DNA sequence analysis, determined that each was identical to one of the two hobo-Notch junctions present in Uc-1. These results are consistent with a model in which hobo-mediated inversions result from homologous pairing and recombination between a pair of hobo elements in reverse orientation.
6
Mahan, M. J., und J. R. Roth. „Ability of a bacterial chromosome segment to invert is dictated by included material rather than flanking sequence.“ Genetics 129, Nr. 4 (01.12.1991): 1021–32. http://dx.doi.org/10.1093/genetics/129.4.1021.
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Abstract Homologous recombination between sequences present in inverse order within the same chromosome can result in inversion formation. We have previously shown that inverse order sequences at some sites (permissive) recombine to generate the expected inversion; no inversions are found when the same inverse order sequences flank other (nonpermissive) regions of the chromosome. In hopes of defining how permissive and nonpermissive intervals are determined, we have constructed a strain that carries a large chromosomal inversion. Using this inversion mutant as the parent strain, we have determined the "permissivity" of a series of chromosomal sites for secondary inversions. For the set of intervals tested, permissivity seems to be dictated by the nature of the genetic material present within the chromosomal interval being tested rather than the flanking sequences or orientation of this material in the chromosome. Almost all permissive intervals include the origin or terminus of replication. We suggest that the rules for recovery of inversions reflect mechanistic restrictions on the occurrence of inversions rather than lethal consequences of the completed rearrangement.
7
Brianti, Mitsue T., Galina Ananina und Louis B. Klaczko. „Differential occurrence of chromosome inversion polymorphisms among Muller's elements in three species of the tripunctata group of Drosophila, including a species with fast chromosomal evolution“. Genome 56, Nr. 1 (Januar 2013): 17–26. http://dx.doi.org/10.1139/gen-2012-0074.
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Detailed chromosome maps with reliable homologies among chromosomes of different species are the first step to study the evolution of the genetic architecture in any set of species. Here, we present detailed photo maps of the polytene chromosomes of three closely related species of the tripunctata group (subgenus Drosophila): Drosophila mediopunctata, D. roehrae, and D. unipunctata. We identified Muller's elements in each species, using FISH, establishing reliable chromosome homologies among species and D. melanogaster. The simultaneous analysis of chromosome inversions revealed a distribution pattern for the inversion polymorphisms among Muller's elements in the three species. Element E is the most polymorphic, with many inversions in each species. Element C follows; while the least polymorphic elements are B and D. While interesting, it remains to be determined how general this pattern is among species of the tripunctata group. Despite previous studies showing that D. mediopunctata and D. unipunctata are phylogenetically closer to each other than to D. roehrae, D. unipunctata shows rare karyotypic changes. It has two chromosome fusions: an additional heterochromatic chromosome pair and a pericentric inversion in the X chromosome. This especial conformation suggests a fast chromosomal evolution that deserves further study.
8
Michailova, Paraskeva, Julia Ilkova, Pavlo Kovalenko, Artem Dzhulai und Iryna Kozeretska. „Long-term retainment of some chromosomal inversions in a local population of Belgica antarctica Jacobs (Diptera, Chironomidae)“. Czech Polar Reports 11, Nr. 1 (24.08.2021): 16–24. http://dx.doi.org/10.5817/cpr2021-1-3.
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Genome of antarctic endemic Belgica antarctica Jacobs has been sequenced. However, no set of inversion diagnostic markers has ever been assigned for the species. Using the classical method of polytene chromosome squash preparation, we found three heterozygous inversions located on the second (two heterozygous inversions) and third chromosomes (one heterozygous inversion) in the Belgica antarctica population of a cape of Wiencke Island, 500 m to SW from Port Lockroy. The chromosome set and chromosome variability did not differ from those described in the literature (Atchley and Davis 1979). Every salivary gland chromosome had its own markers by which it can be determined. However, we did not find a sex-linked inversion on chromosome III and heterozygous inversion on chromosome I, reported in earlier studies. For the first time, we observed a strong heterochromatin band in chromosome III at the telomere of one arm. Our data show not only the stability of the described inversions in the population but also the usefulness of the squash preparation technique in the studies of genetic variability of Belgica antarctica in present time.
9
Miesel, L., A. Segall und J. R. Roth. „Construction of chromosomal rearrangements in Salmonella by transduction: inversions of non-permissive segments are not lethal.“ Genetics 137, Nr. 4 (01.08.1994): 919–32. http://dx.doi.org/10.1093/genetics/137.4.919.
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Abstract Homologous sequences placed in inverse order at particular separated sites in the bacterial chromosome (termed "permissive") can recombine to form an inversion of the intervening chromosome segment. When the same repeated sequences flank other chromosome segments ("non-permissive"), recombination occurs but the expected inversion rearrangement is not found among the products. The failure to recover inversions of non-permissive chromosomal segments could be due to lethal effects of the final rearrangement. Alternatively, local chromosomal features might pose barriers to reciprocal exchanges between sequences at particular sites and could thereby prevent formation of inversions of the region between such sites. To distinguish between these two possibilities, we have constructed inversions of two non-permissive intervals by means of phage P22-mediated transduction crosses. These crosses generate inversions by simultaneous incorporation of two transduced fragments, each with a sequence that forms one join-point of the final inversion. We constructed inversions of the non-permissive intervals trp ('34) to his ('42) and his ('42) to cysA ('50). Strains with the constructed inversions are viable and grow normally. These results show that our previous failure to detect formation of these inversions by recombination between chromosomal sequences was not due to lethal effects of the final rearrangement. We infer that the "non-permissive" character of some chromosomal segments reflects the inability of the recombination system to perform the needed exchanges between inverse order sequences at particular sites. Apparently these mechanistic problems were circumvented by the transductional method used here to direct inversion formation.
10
Coyne, J. A., W. Meyers, A. P. Crittenden und P. Sniegowski. „The fertility effects of pericentric inversions in Drosophila melanogaster.“ Genetics 134, Nr. 2 (01.06.1993): 487–96. http://dx.doi.org/10.1093/genetics/134.2.487.
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Abstract Heterozygotes for pericentric inversions are expected to be semisterile because recombination in the inverted region produces aneuploid gametes. Newly arising pericentric inversions should therefore be quickly eliminated from populations by natural selection. The occasional polymorphism for such inversions and their fixation among closely related species have supported the idea that genetic drift in very small populations can overcome natural selection in the wild. We studied the effect of 7 second-chromosome and 30 third-chromosome pericentric inversions on the fertility of heterokaryotypic Drosophila melanogaster females. Surprisingly, fertility was not significantly reduced in many cases, even when the inversion was quite large. This lack of underdominance is almost certainly due to suppressed recombination in inversion heterozygotes, a phenomenon previously observed in Drosophila. In the large sample of third-chromosome inversions, the degree of underdominance depends far more on the position of breakpoints than on the inversion's length. Analysis of these positions shows that this chromosome has a pair of "sensitive sites" near cytological divisions 68 and 92: these sites appear to reduce recombination in a heterozygous inversion whose breakpoints are nearby. There may also be "sensitive sites" near divisions 31 and 49 on the second chromosome. Such sites may be important in initiating synapsis. Because many pericentric inversions do not reduce the fertility of heterozygotes, we conclude that the observed fixation or polymorphism of such rearrangements in nature does not imply genetic drift in very small populations.
11
Singh, B. N., und A. K. Singh. „The effects of heterozygous inversions on crossing-over in Drosophila ananassae“. Genome 29, Nr. 5 (01.10.1987): 802–5. http://dx.doi.org/10.1139/g87-134.
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Crossing-over was studied in females of Drosophila ananassae under different karyotypic combinations to detect the effects of heterozygous inversions by utilizing three recessive markers of the second chromosome. Because of the presence of a subterminal inversion (2L) in the heterozygous condition, crossing-over between the cu and b genes is completely eliminated. However, 2L heterozygosity enhances the level of recombination between the b and se genes. Furthermore, two third chromosome inversions when heterozygous also exert an enhancing effect on crossing-over in the second chromosome. These results provide evidence for the existence of intra- and inter-chromosomal effects of inversions on crossing-over in D. ananassae. Key words: Drosophila ananassae, crossing-over, inversions, intrachromosomal effects, interchromosomal effects.
12
Das, Aparup, und B. N. Singh. „Genetic differentiation and inversion clines in Indian natural populations of Drosophila melanogaster“. Genome 34, Nr. 4 (01.08.1991): 618–25. http://dx.doi.org/10.1139/g91-094.
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To study the genetic differentiation and inversion clines in Indian natural populations of Drosophila melanogaster, 14 natural populations (6 from the north and 8 from the south) were screened for chromosome inversions. The chromosomal analysis revealed the presence of 23 paracentric inversions, which include 4 common cosmopolitan, 4 rare cosmopolitan, 2 recurrent endemic, and 13 unique endemic (new inversions detected for the first time) inversions. The difference in karyotype frequencies between populations from the north and south were highly significant and the level of inversion heterozygosity was higher in populations from the south. Statistically significant negative correlations were found between each of the four common cosmopolitan inversions and latitude. These findings are in accord with results from other worldwide geographic regions and show that Indian populations of D. melanogaster have undergone considerable genetic differentiation at the level of inversion polymorphism.Key words: Drosophila melanogaster, Indian natural populations, chromosome inversions, genetic differentiation, north–south clines.
13
Salceda, Victor. „A prospective study of inversion polymorphism in natural populations of two Drosophila species from eastern Mexico“. Genetika 42, Nr. 3 (2010): 407–14. http://dx.doi.org/10.2298/gensr1003407s.
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Relative frequencies for heterozygous inversions in nine populations of D. nebulosa and six of D. willistoni were analyzed. The analysis corresponds to a grand total of 1828 arm chromosomes in which their genotype were determined, of them 404 correspond for each one of the two polymorphic chromosomes, X and III, of D. nebulosa and 204 per chromosome arm in D. willistoni. The more abundant inversions, according to their relative frequencies in D. nebulosa were the XL inversion with 7.9 % and inversion ?A? in the third chromosome with 15.6 %, the remaining inversion found did not reach the ten percent. In the case of D. willistoni the more frequent inversions were for the XL arm inversions ?A? and ?D? with 13.7 and 12.2 percent respectively the remaining five did not reach a ten percent; in the XR arm the higher frequencies were for inversions ?D? and ?E? with 9.3 % each been the other four inversions with values less than five percent; in the IIL arm none of the seven inversions registered had values higher than six percent; inversion ?E? in the IIR arm showed a frequency of 24.5 % and the five remaining barely reached a frequency of 5 %; among the 12 different inversions recorded in the third chromosome, only inversion ?B? surpassed the ten percent in this case with 16.1 %. We must mention that the Standar sequence in all cases, for both species, always had high frequencies as shown in Tables II and III. The corresponding variability for this characteristic is for D. nebulosa 61.4 %.and 72.2% for D.willitoni. Concerning other parameter observed we have the average number of inversions per female in our case for D. nebulosa was 1.4 and for D. willistoni 3.6 which indicate the both species are marginal with respect to the distribution of this character in both species since in the central areas of distribution reach values up to nine inversions per female.
14
della Torre, A., L. Merzagora, J. R. Powell und M. Coluzzi. „Selective Introgression of Paracentric Inversions Between Two Sibling Species of the Anopheles gambiae Complex“. Genetics 146, Nr. 1 (01.05.1997): 239–44. http://dx.doi.org/10.1093/genetics/146.1.239.
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The Anopheles gambiae complex includes the major vectors of malaria in sub-Saharan Africa where >80% of all world-wide cases occur. These mosquitoes are characterized by chromosomal inversions associated to the speciation process and to intraspecific ecological and behavioral flexibility. It has been postulated that introgressive hybridization has selectively transferred inversions on the second chromosome between A. gambiae and A. arabiensis, the two most important vectors of malaria. Here we directly test this hypothesis with laboratory experiments in which hybrid populations were established and the fate of chromosomal inversions were followed. Consistent with the hypothesis, “foreign” X chromosomes were eliminated within two generations, while some “foreign” second chromosomes persisted for the duration of the experiments and, judging from the excess of heterozygotes, established stable heterotic polymorphisms. Only those second chromosome inversions found naturally in the species could be introgressed.
15
Kuvangkadilok, Chaliow, Suwannee Phayuhasena und Visut Baimai. „Population cytogenetic studies on Simulium feuerborni Edwards (Diptera: Simuliidae) from northern Thailand“. Genome 42, Nr. 1 (01.02.1999): 80–86. http://dx.doi.org/10.1139/g98-106.
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A standard photographic map of Simulium feuerborni (Diptera: Simuliidae) was constructed from larval salivary gland polytene chromosomes and is described herein. Analysis of polytene chromosomes was made from wild larvae collected from the four populations at Doi Inthanon National Park, Chiang Mai Province, northern Thailand. Simulium feuerborni has three pairs of chromosomes (2n = 6) which are arranged from the longest to the shortest. Chromosome I is metacentric while chromosomes II and III are submetacentric. A total of six simple paracentric inversions have been detected in these natural populations of S. feuerborni. These inversions (IS-1, IL-1, IIL-1, IIL-2, IIIS-1, IIIL-1) occurred in all chromosome arms except for the arm IIS. Significant deviation from Hardy-Weinberg equilibrium has been observed in inversion IIIL-1 at Hui Sai Luaeng suggesting the existence of two gene pools in this population. There is no indication of sex linkage associated with an inversion sequence in these populations. Thus, the X and Y chromosomes of S. feuerborni could not be recognized in this study.Key words: Simulium, polytene chromosome map, inversion polymorphisms
16
Haglund, U., G. Juliusson, B. Stellan und G. Gahrton. „Hairy cell leukemia is characterized by clonal chromosome abnormalities clustered to specific regions“. Blood 83, Nr. 9 (01.05.1994): 2637–45. http://dx.doi.org/10.1182/blood.v83.9.2637.2637.
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Abstract Cytogenetic analysis was performed on B-cell mitogen-stimulated cells from 36 patients with symptomatic hairy cell leukemia. Evaluable metaphases were achieved from 30 patients, and (67%) showed clonal abnormalities. Recurrent chromosomal aberrations involving chromosomes 1, 2, 5, 6, 11, 19, and 20 were found. The abnormalities were mostly deletions and inversions, whereas translocations and numerical abnormalities, except trisomy 5, were rare. Fourteen patients showed multiple clones, which mostly were unrelated and found in different combinations in individual cells. Cells with non-clonal abnormalities identical to those found in clonal changes in other patients were common. Chromosome 5 was involved in clonal aberrations in 12 of 30 (40%) patients, most commonly as trisomy 5 (n = 4), or pericentric inversions (n = 6) and interstitial deletions (n = 4) involving band 5q13. Three patients showed two and 1 patient three different clones that involved chromosome 5. In addition, 1 patient had a rare constitutional inversion of chromosome 5 with breakpoints at p13.1 and q13.3. Pericentric inversions and interstitial deletions of chromosome 2 occurred clonally in 4 patients (13%) and in single cells of another 6 patients. Deletions of chromosome 1 at band q42 was found in 5 patients, and 1 patient had a translocation between 1q42 and a supernumerary chromosome 5. Deletions of 6q and 11q were similar to those commonly found in other lymphoproliferative disorders. Trisomy 5, structural abnormalities involving the pericentromeric regions of chromosomes 5 and 2, and 1q42 abnormalities were findings distinguishing the karyotypes in hairy cell leukemia from those of other hematologic malignancies.
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Haglund, U., G. Juliusson, B. Stellan und G. Gahrton. „Hairy cell leukemia is characterized by clonal chromosome abnormalities clustered to specific regions“. Blood 83, Nr. 9 (01.05.1994): 2637–45. http://dx.doi.org/10.1182/blood.v83.9.2637.bloodjournal8392637.
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Cytogenetic analysis was performed on B-cell mitogen-stimulated cells from 36 patients with symptomatic hairy cell leukemia. Evaluable metaphases were achieved from 30 patients, and (67%) showed clonal abnormalities. Recurrent chromosomal aberrations involving chromosomes 1, 2, 5, 6, 11, 19, and 20 were found. The abnormalities were mostly deletions and inversions, whereas translocations and numerical abnormalities, except trisomy 5, were rare. Fourteen patients showed multiple clones, which mostly were unrelated and found in different combinations in individual cells. Cells with non-clonal abnormalities identical to those found in clonal changes in other patients were common. Chromosome 5 was involved in clonal aberrations in 12 of 30 (40%) patients, most commonly as trisomy 5 (n = 4), or pericentric inversions (n = 6) and interstitial deletions (n = 4) involving band 5q13. Three patients showed two and 1 patient three different clones that involved chromosome 5. In addition, 1 patient had a rare constitutional inversion of chromosome 5 with breakpoints at p13.1 and q13.3. Pericentric inversions and interstitial deletions of chromosome 2 occurred clonally in 4 patients (13%) and in single cells of another 6 patients. Deletions of chromosome 1 at band q42 was found in 5 patients, and 1 patient had a translocation between 1q42 and a supernumerary chromosome 5. Deletions of 6q and 11q were similar to those commonly found in other lymphoproliferative disorders. Trisomy 5, structural abnormalities involving the pericentromeric regions of chromosomes 5 and 2, and 1q42 abnormalities were findings distinguishing the karyotypes in hairy cell leukemia from those of other hematologic malignancies.
18
María, José, Carmen Segarra und Alfredo Ruiz. „Chromosomal Homology and Molecular Organization of Muller's Elements D and E in the Drosophila repleta Species Group“. Genetics 145, Nr. 2 (01.02.1997): 281–95. http://dx.doi.org/10.1093/genetics/145.2.281.
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Thirty-three DNA clones containing protein-coding genes have been used for in situ hybridization to the polytene chromosomes of two Drosophila repleta group species, D. repleta and D. buzzatii. Twenty-six clones gave positive results allowing the precise localization of 26 genes and the tentative identification of another nine. The results were fully consistent with the currently accepted chromosomal homologies and in no case was evidence for reciprocal translocations or pericentric inversions found. Most of the genes mapped to chromosomes 2 and 4 that are homologous, respectively, to chromosome arms 3R and 3L of D. melanogaster (Muller's elements E and D). The comparison of the molecular organization of these two elements between D. melanogaster and D. repleta (two species that belong to different subgenera and diverged some 62 million years ago) showed an extensive reorganization via paracentric inversions. Using a maximum likelihood procedure, we estimated that 130 paracentric inversions have become fixed in element E after the divergence of the two lineages. Therefore, the evolution rate for element E is approximately one inversion per million years. This value is comparable to previous estimates of the rate of evolution of chromosome X and yields an estimate of 4.5 inversions per million years for the whole Drosophila genome.
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Naumenko, Anastasia N., Dmitriy A. Karagodin, Andrey A. Yurchenko, Anton V. Moskaev, Olga I. Martin, Elina M. Baricheva, Igor V. Sharakhov, Mikhail I. Gordeev und Maria V. Sharakhova. „Chromosome and Genome Divergence between the Cryptic Eurasian Malaria Vector-Species Anopheles messeae and Anopheles daciae“. Genes 11, Nr. 2 (05.02.2020): 165. http://dx.doi.org/10.3390/genes11020165.
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Chromosomal inversions are important drivers of genome evolution. The Eurasian malaria vector Anopheles messeae has five polymorphic inversions. A cryptic species, An. daciae, has been discriminated from An. messeae based on five fixed nucleotide substitutions in the internal transcribed spacer 2 (ITS2) of ribosomal DNA. However, the inversion polymorphism in An. daciae and the genome divergence between these species remain unexplored. In this study, we sequenced the ITS2 region and analyzed the inversion frequencies of 289 Anopheles larvae specimens collected from three locations in the Moscow region. Five individual genomes for each of the two species were sequenced. We determined that An. messeae and An. daciae differ from each other by the frequency of polymorphic inversions. Inversion X1 was fixed in An. messeae but polymorphic in An. daciae populations. The genome sequence comparison demonstrated genome-wide divergence between the species, especially pronounced on the inversion-rich X chromosome (mean Fst = 0.331). The frequency of polymorphic autosomal inversions was higher in An. messeae than in An. daciae. We conclude that the X chromosome inversions play an important role in the genomic differentiation between the species. Our study determined that An. messeae and An. daciae are closely related species with incomplete reproductive isolation.
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Zhao, J. T., M. Frommer, J. A. Sved und A. Zacharopoulou. „Mitotic and polytene chromosome analyses in the Queensland fruit fly, Bactrocera tryoni (Diptera: Tephritidae)“. Genome 41, Nr. 4 (01.08.1998): 510–26. http://dx.doi.org/10.1139/g98-053.
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The Queensland fruit fly, Bactrocera tryoni, like the Mediterranean fruit fly, Ceratitis capitata, has a diploid complement of 12 chromosomes, including five pairs of autosomes and a XX/XY sex chromosome pair. Characteristic features of each chromosome are described. Chromosomal homology between B. tryoni and C. capitata has been determined by comparing chromosome banding pattern and in situ hybridisation of cloned genes to polytene chromosomes. Although the evidence indicates that a number of chromosomal inversions have occurred since the separation of the two species, synteny of the chromosomes appears to have been maintained.Key words: tephritid fruit fly, Bactrocera tryoni, polytene chromosomes, in situ hybridisation, chromosomal homology.
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da Silva, Vinicius H., Veronika N. Laine, Mirte Bosse, Lewis G. Spurgin, Martijn F. L. Derks, Kees van Oers, Bert Dibbits et al. „The Genomic Complexity of a Large Inversion in Great Tits“. Genome Biology and Evolution 11, Nr. 7 (22.05.2019): 1870–81. http://dx.doi.org/10.1093/gbe/evz106.
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Abstract Chromosome inversions have clear effects on genome evolution and have been associated with speciation, adaptation, and the evolution of the sex chromosomes. In birds, these inversions may play an important role in hybridization of species and disassortative mating. We identified a large (≈64 Mb) inversion polymorphism in the great tit (Parus major) that encompasses almost 1,000 genes and more than 90% of Chromosome 1A. The inversion occurs at a low frequency in a set of over 2,300 genotyped great tits in the Netherlands with only 5% of the birds being heterozygous for the inversion. In an additional analysis of 29 resequenced birds from across Europe, we found two heterozygotes. The likely inversion breakpoints show considerable genomic complexity, including multiple copy number variable segments. We identified different haplotypes for the inversion, which differ in the degree of recombination in the center of the chromosome. Overall, this remarkable genetic variant is widespread among distinct great tit populations and future studies of the inversion haplotype, including how it affects the fitness of carriers, may help to understand the mechanisms that maintain it.
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King, M. „Chromosomal Evolution in the Diplodactylinae (Gekkonidae, Reptilia) .1. Evolutionary Relationships and Patterns of Change“. Australian Journal of Zoology 35, Nr. 5 (1987): 507. http://dx.doi.org/10.1071/zo9870507.
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A chromosomal analysis of 47 species of diplodactyline gekkos indicates that these are a monophyletic assemblage derived from a 2n = 38 acrocentric ancestral karyotype. Four major clades are present, the first possessing the ancestral karyotype. The remainder are defined by the possession of a series of shared derived chromosomal rearrangements, or by the type of chromosome change. The first of these derived clades includes the subgenus Strophurus, which has five fixed, presumed pericentric inversion differences. The second includes members of the D. vittatus species group. Here, a number of chromosome fusions have been established which appear to have been associated with speciation. The third derived clade is distinguished by 19 fixed, presumed pericentric inversions, and includes the genera, Oedura, Rhacodactylus, Bavayia, Pseudothecadactylus, Carphodactylus and Hoplodactylus. It is argued that the 2n=38 acrocentric karyotype common to many of the species is the ancestral karyomorph, and the modifications of this format have been achieved by both chromosome fusion and pericentric inversion. The decision that this is the ancestral karyomorph was based on its dominance in extant species; the fact that similar karyotypes are present in other gekkonid subfamilies (effective out-groups), that 2n =38 all acrocentric ancestral karyotypes are also found in some other lizard families, and that such a diversity of rearrangements was established, provide arguments against any other viable ancestral format. Two discrete modes of chromosomal repatterning are found in the Diplodactylinae: the fixation of presumptive multiple pericentric inversions, producing a karyomorph which characterises large groups of species; and the fixation of fusion or presumptive inversion differences which distinguish individual species or chromosome races. The latter appear to have been associated with speciation. It is clear that in certain groups, such as the Strophurus species group (the members of which all share a derived karyomorph defined by the presence of five inverted chromosomes), speciation has proceeded without gross chromosomal rearrangements.
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McGaugh, Suzanne E., und Mohamed A. F. Noor. „Genomic impacts of chromosomal inversions in parapatric Drosophila species“. Philosophical Transactions of the Royal Society B: Biological Sciences 367, Nr. 1587 (05.02.2012): 422–29. http://dx.doi.org/10.1098/rstb.2011.0250.
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Chromosomal inversions impact genetic variation and facilitate speciation in part by reducing recombination in heterokaryotypes. We generated multiple whole-genome shotgun sequences of the parapatric species pair Drosophila pseudoobscura and Drosophila persimilis and their sympatric outgroup ( Drosophila miranda ) and compared the average pairwise differences for neutral sites within, just outside and far outside of the three large inversions. Divergence between D. pseudoobscura and D. persimilis is high inside the inversions and in the suppressed recombination regions extending 2.5 Mb outside of inversions, but significantly lower in collinear regions further from the inversions. We observe little evidence of decreased divergence predicted to exist in the centre of inversions, suggesting that gene flow through double crossovers or gene conversion is limited within the inversion, or selection is acting within the inversion to maintain divergence in the face of gene flow. In combination with past studies, we provide evidence that inversions in this system maintain areas of high divergence in the face of hybridization, and have done so for a substantial period of time. The left arm of the X chromosome and chromosome 2 inversions appear to have arisen in the lineage leading to D. persimilis approximately 2 Ma, near the time of the split of D. persimilis–D. pseudoobscura–D. miranda , but likely fixed within D. persimilis much more recently, as diversity within D. persimilis is substantially reduced inside and near these two inversions. We also hypothesize that the inversions in D. persimilis may provide an empirical example of the ‘mixed geographical mode’ theory of inversion origin and fixation, whereby allopatry and secondary contact both play a role.
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Poopittayasataporn, Anan, und Visut Baimai. „Polytene chromosome relationships of five species of the Anopheles dirus complex in Thailand“. Genome 38, Nr. 3 (01.06.1995): 426–34. http://dx.doi.org/10.1139/g95-056.
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Photographic maps and rearrangements of each salivary gland polytene chromosome arm of Anopheles nemophilous (species F) and of An. dirus species A, B, C, and D of the Dirus group from natural populations in Thailand are presented. Structural conformation of heterokaryotypes and comparison of chromosome banding sequences reveal 10 paracentric inversions. The data on fixed inversion of 3Rb and inversion polymorphism of the X chromosome shared by these species were used to construct a phylogeny of the five members of the An. dirus complex, thereby outlining their patterns of speciation through chromosomal rearrangements.Key words: polytene chromosome rearrangements, Anopheles dirus, phylogeny.
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Qi, Lili, Bend Friebe und Bikram S. Gill. „Complex genome rearrangements reveal evolutionary dynamics of pericentromeric regions in the Triticeae“. Genome 49, Nr. 12 (Dezember 2006): 1628–39. http://dx.doi.org/10.1139/g06-123.
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Most pericentromeric regions of eukaryotic chromosomes are heterochromatic and are the most rapidly evolving regions of complex genomes. The closely related genomes within hexaploid wheat ( Triticum aestivum L., 2n = 6x = 42, AABBDD), as well as in the related Triticeae taxa, share large conserved chromosome segments and provide a good model for the study of the evolution of pericentromeric regions. Here we report on the comparative analysis of pericentric inversions in the Triticeae, including Triticum aestivum, Aegilops speltoides , Ae. longissima, Ae. searsii, Hordeum vulgare , Secale cereale , and Agropyron elongatum . Previously, 4 pericentric inversions were identified in the hexaploid wheat cultivar ‘Chinese Spring’ (‘CS’) involving chromosomes 2B, 4A, 4B, and 5A. In the present study, 2 additional pericentric inversions were detected in chromosomes 3B and 6B of ‘CS’ wheat. Only the 3B inversion pre-existed in chromosome 3S, 3Sl, and 3Ss of Aegilops species of the Sitopsis section, the remaining inversions occurring after wheat polyploidization. The translocation T2BS/6BS previously reported in ‘CS’ was detected in the hexaploid variety ‘Wichita’ but not in other species of the Triticeae. It appears that the B genome is more prone to genome rearrangements than are the A and D genomes. Five different pericentric inversions were detected in rye chromosomes 3R and 4R, 4Sl of Ae. longissima, 4H of barley, and 6E of Ag. elongatum. This indicates that pericentric regions in the Triticeae, especially those of group 4 chromosomes, are undergoing rapid and recurrent rearrangements.
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Ma, Jian, Shang Gao, Jiri Stiller, Qian-Tao Jiang, Xiu-Jin Lan, Ya-Xi Liu, Zhi-En Pu, Jirui Wang, Yuming Wei und You-Liang Zheng. „Identification of genes bordering breakpoints of the pericentric inversions on 2B, 4B, and 5A in bread wheat (Triticum aestivum L.)“. Genome 58, Nr. 8 (August 2015): 385–90. http://dx.doi.org/10.1139/gen-2015-0060.
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Chromosome translocation is an important driving force in shaping genomes during evolution. Detailed knowledge of chromosome translocations in a given species and its close relatives should increase the efficiency and precision of chromosome engineering in crop improvement. To identify genes flanking the breakpoints of translocations and inversions as a step toward identifying breakpoints in bread wheat, we systematically analysed genes in the Brachypodium genome against wheat survey sequences and bin-mapped ESTs (expressed sequence tags) derived from the hexaploid wheat genotype ‘Chinese Spring’. In addition to those well-known translocations between group 4, 5, and 7 chromosomes, this analysis identified genes flanking the three pericentric inversions on chromosomes 2B, 4B, and 5A. However, numerous chromosomal rearrangements reported in early studies could not be confirmed. The genes flanking the breakpoints reported in this study are valuable for isolating these breakpoints.
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Sharakhov, Igor V., Gleb N. Artemov und Maria V. Sharakhova. „Chromosome evolution in malaria mosquitoes inferred from physically mapped genome assemblies“. Journal of Bioinformatics and Computational Biology 14, Nr. 02 (April 2016): 1630003. http://dx.doi.org/10.1142/s0219720016300033.
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Polymorphic inversions in mosquitoes are distributed nonrandomly among chromosomes and are associated with ecological, behavioral, and physiological adaptations related to pathogen transmission. Despite their significance, the patterns and mechanism of genome rearrangements are not well understood. Recent sequencing and physical mapping of the genomes for 16 Anopheles mosquito species provided an opportunity to study chromosome evolution at the highest resolution. New studies revealed that fixed rearrangement accumulated [Formula: see text]3 times faster on the X chromosome than on autosomes. The highest densities of transposable elements (TEs) and satellites of different sizes have also been found on the X chromosome, suggesting a mechanism for the inversion generation. The high rate of X chromosome rearrangements is in sharp contrast with the paucity of polymorphic inversions on the X in the majority of anopheline species. This paper highlights the advances in understanding chromosome evolution in malaria vectors and discusses possible future directions in studying mechanisms and biological roles of genome rearrangements.
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Tanksley, S. D., M. W. Ganal, J. P. Prince, M. C. de Vicente, M. W. Bonierbale, P. Broun, T. M. Fulton, J. J. Giovannoni, S. Grandillo und G. B. Martin. „High density molecular linkage maps of the tomato and potato genomes.“ Genetics 132, Nr. 4 (01.12.1992): 1141–60. http://dx.doi.org/10.1093/genetics/132.4.1141.
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Abstract High density molecular linkage maps, comprised of more than 1000 markers with an average spacing between markers of approximately 1.2 cM (ca. 900 kb), have been constructed for the tomato and potato genomes. As the two maps are based on a common set of probes, it was possible to determine, with a high degree of precision, the breakpoints corresponding to 5 chromosomal inversions that differentiate the tomato and potato genomes. All of the inversions appear to have resulted from single breakpoints at or near the centromeres of the affected chromosomes, the result being the inversion of entire chromosome arms. While the crossing over rate among chromosomes appears to be uniformly distributed with respect to chromosome size, there is tremendous heterogeneity of crossing over within chromosomes. Regions of the map corresponding to centromeres and centromeric heterochromatin, and in some instances telomeres, experience up to 10-fold less recombination than other areas of the genome. Overall, 28% of the mapped loci reside in areas of putatively suppressed recombination. This includes loci corresponding to both random, single copy genomic clones and transcribed genes (detected with cDNA probes). The extreme heterogeneity of crossing over within chromosomes has both practical and evolutionary implications. Currently tomato and potato are among the most thoroughly mapped eukaryotic species and the availability of high density molecular linkage maps should facilitate chromosome walking, quantitative trait mapping, marker-assisted breeding and evolutionary studies in these two important and well studied crop species.
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Livingston, Gordon K., Terri L. Ryan, Tammy L. Smith, Maria B. Escalona, Alvis E. Foster und Adayabalam S. Balajee. „Detection of Simple, Complex, and Clonal Chromosome Translocations Induced by Internal Radioiodine Exposure: A Cytogenetic Follow-Up Case Study after 25 Years“. Cytogenetic and Genome Research 159, Nr. 4 (2019): 169–81. http://dx.doi.org/10.1159/000504689.
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Here, we report the findings of a 25-year cytogenetic follow-up study on a male patient who received 2 rounds of radioiodine treatment within a span of 26 months (1.78 GBq in 1992 and 14.5 GBq in 1994). The patient was 34 years old with a body mass index of 25 at the time of the first radioiodine treatment. Multicolor FISH and multicolor banding (mBAND) techniques performed on the patient detected inter- and intrachromosomal exchanges. Although the frequency of chromosome translocations remained essentially the same as reported in our earlier study (0.09/cell), the percentage of reciprocal (balanced) translocations increased from 54.38 to 80.30% in the current study. In addition to simple chromosome translocations, complex exchanges (0.29%) involving more than 2 chromosomes were detected for the first time in this patient. Strikingly, a clonal translocation involving chromosomes 14 and 15, t(14p;15q), was found in 7 of the 677 cells examined (1.03%). The presence of complex and clonal translocations indicates the onset of chromosomal instability induced by internal radioiodine exposure. mBAND analysis using probes specific for chromosomes 1, 2, 4, 5, and 10 revealed 5 inversions in a total of 717 cells (0.69%), and this inversion frequency is several-fold higher than the baseline frequency reported in healthy individuals using the classical G-banding technique. Collectively, our study suggests that stable chromosome aberrations such as translocations and inversions can be useful not only for retrospective biodosimetry but also for long-term monitoring of chromosomal instability caused by past radioiodine exposure.
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Shields, Gerald F. „Interchange chromosomes in Simulium nigricoxum Stone Diptera: Simuliidae“. Genome 33, Nr. 5 (01.10.1990): 683–85. http://dx.doi.org/10.1139/g90-102.
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A whole-arm interchange (IS-IIIL/IL-IIIS) is described from a larval population of Simulium nigricoxum Stone in the Yukon Territory. Although unstudied elsewhere, S. nigricoxum appears to differ from its closest presumed relative, Simulium malyschevi, by the whole-arm interchange, a fixed autosomal inversion in the short arm of the second chromosome, and a sex-linked inversion also in the short arm of the second chromosome. It is possible that the interchange provided a chromosomal basis for reproductive isolation of S. nigricoxum from an ancestral form, but because of its apparent localized distribution that hypothesis must remain tentative.Key words: Simulium nigricoxum, Simulium malyschevi, chromosome interchanges, inversions, reproductive isolation.
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Eanes, Walter F., Cedric Wesley und Brian Charlesworth. „Accumulation of P elements in minority inversions in natural populations of Drosophila melanogaster“. Genetical Research 59, Nr. 1 (Februar 1992): 1–9. http://dx.doi.org/10.1017/s0016672300030111.
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SummaryThe accumulation of a transposable element inside chromosomal inversions is examined theoretically by a mathematical model, and empirically by counts of P elements associated with inversion polymorphisms in natural populations of Drosophila melanogaster. The model demonstrates that, if heterozygosity for an inversion effectively reduces element associated production of detrimental chromosome rearrangements, a differential accumulation of elements is expected, with increased copy number inside the minority inversion. Several-fold differential accumulations are possible with certain parameter values. We present data on P element counts for inversion polymorphisms on all five chromosome arms of 157 haploid genomes from two African populations. Our observations show significantly increased numbers of elements within the regions associated with the least common, or minority arrangements, in natural inversion polymorphisms.
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THAPA, SACHIN, PETER H. ADLER, SHAILIKA CHHETRI, RAKESH VARMA und WILLIE HENRY. „Chromosomal evidence for a new cryptic species of black fly in the Simulium praelargum complex (Diptera: Simuliidae) from West Bengal, India“. Zootaxa 4244, Nr. 1 (17.03.2017): 137. http://dx.doi.org/10.11646/zootaxa.4244.1.8.
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Analyses of polytene chromosomes revealed a new cryptic species of black fly, Simulium praelargum “IL”, in the Simulium (Nevermania) feuerborni group from Darjeeling, West Bengal, India. This new species occurred sympatrically with two other previously recognized species in the S. praelargum complex: Simulium praelargum Datta sensu stricto and Simulium praelargum “IIIL-1.2”. Chromosome arms IS, IIS, IIL, and IIIS of the new species showed no differences in banding patterns, compared with the sequences in Simulium praelargum s. s. and Simulium praelargum “IIIL-1.2”. Chromosome arm IIIL of the new species was identical to that of S. praelargum s. s., but differed from that of S. praelargum “IIIL-1.2” by two fixed inversions. Chromosome arm IL of the new species differed from that of both species by four fixed inversions: IL-1, IL-2, IL-3, and IL-4. The new species and S. praelargum s. s. lacked a chromocenter, which was present in S. praelargum “IIIL-1.2”. Sex chromosomes of the new species were cytologically undifferentiated (X0X0, X0Y0) and all specimens were monomorphic for autosomal inversion polymorphisms. Speciation in the S. feuerborni group, unlike in many other simuliid taxa, did not involve cytological differentiation of sex chromosomes.
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Gokhman, Vladimir E., Kristen L. Kuhn, James B. Woolley und Keith R. Hopper. „Variation in genome size and karyotype among closely related aphid parasitoids (Hymenoptera, Aphelinidae)“. Comparative Cytogenetics 11, Nr. 1 (23.02.2017): 97–117. http://dx.doi.org/10.3897/compcytogen.v11i1.10872.
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Genome sizes were measured and determined for the karyotypes of nine species of aphid parasitoids in the genusAphelinusDalman,1820. Large differences in genome size and karyotype were found betweenAphelinusspecies, which is surprising given the similarity in their morphology and life history. Genome sizes estimated from flow cytometry were larger for species in theAphelinusmali(Haldeman, 1851) complex than those for the species in theAphelinusdaucicolaKurdjumov, 1913 andAphelinusvaripes(Förster,1841) complexes. Haploid karyotypes of theAphelinusdaucicolaandAphelinusmalicomplexes comprised five metacentric chromosomes of similar size, whereas those of theAphelinusvaripescomplex had four chromosomes, including a larger and a smaller metacentric chromosome and two small acrocentric chromosomes or a large metacentric and three smaller acrocentric chromosomes. Total lengths of female haploid chromosome sets correlated with genome sizes estimated from flow cytometry. Phylogenetic analysis of karyotypic variation revealed a chromosomal fusion together with pericentric inversions in the common ancestor of theAphelinusvaripescomplex and further pericentric inversions in the clade comprisingAphelinuskurdjumoviMercet, 1930 andAphelinushordeiKurdjumov, 1913. Fluorescencein situhybridization with a 28S ribosomal DNA probe revealed a single site on chromosomes of the haploid karyotype ofAphelinuscoreaeHopper & Woolley, 2012. The differences in genome size and total chromosome length between species complexes matched the phylogenetic divergence between them.
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Proskuryakova, Kulemzina, Perelman, Yudkin, Lemskaya, Okhlopkov, Kirillin et al. „Comparative Chromosome Mapping of Musk Ox and the X Chromosome among Some Bovidae Species“. Genes 10, Nr. 11 (29.10.2019): 857. http://dx.doi.org/10.3390/genes10110857.
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: Bovidae, the largest family in Pecora infraorder, are characterized by a striking variability in diploid number of chromosomes between species and among individuals within a species. The bovid X chromosome is also remarkably variable, with several morphological types in the family. Here we built a detailed chromosome map of musk ox (Ovibos moschatus), a relic species originating from Pleistocene megafauna, with dromedary and human probes using chromosome painting. We trace chromosomal rearrangements during Bovidae evolution by comparing species already studied by chromosome painting. The musk ox karyotype differs from the ancestral pecoran karyotype by six fusions, one fission, and three inversions. We discuss changes in pecoran ancestral karyotype in the light of new painting data. Variations in the X chromosome structure of four bovid species nilgai bull (Boselaphus tragocamelus), saola (Pseudoryx nghetinhensis), gaur (Bos gaurus), and Kirk’s Dikdik (Madoqua kirkii) were further analyzed using 26 cattle BAC-clones. We found the duplication on the X in saola. We show main rearrangements leading to the formation of four types of bovid X: Bovinae type with derived cattle subtype formed by centromere reposition and Antilopinae type with Caprini subtype formed by inversion in XSB3.
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Singh, A. K., und B. N. Singh. „Heterozygous inversions and spontaneous male crossing-over in Drosophila ananassae“. Genome 30, Nr. 3 (01.06.1988): 445–50. http://dx.doi.org/10.1139/g88-075.
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Experiments were conducted to detect the effects of heterozygous inversions on spontaneous crossing-over in males of Drosophila ananassae by using a second chromosome triple recessive stock and four wild stocks. The karyotypic constitution of all the stocks was known. The occurrence of spontaneous male crossing-over has been observed in all the strains tested though the rate of recombination varies. The results show that crossing-over is completely absent between cu and b genes due to inversion heterozygosity in 2L. The males homozygous in 2L show crossing-over in both regions (cu–b, b–se). The inversion heterozygosity in 2L increases the rate of recombination between b and se genes. Furthermore, two third chromosome inversions, when heterozygous also increase crossing-over in the second chromosome. These results suggest that spontaneous male crossing-over in D. ananassae is affected by heterozygous inversions. Thus the present finding lends support to the earlier suggestion that spontaneous crossing-over in males of D. ananassae is meiotic in origin.Key words: Drosophila ananassae, heterozygous inversions, spontaneous male crossing-over.
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Spironello, Mike, und Fiona F. Hunter. „An intra- and inter-island study of the polytene chromosomes of Simulium exasperans (Diptera: Simuliidae)“. Canadian Journal of Zoology 82, Nr. 5 (01.05.2004): 808–16. http://dx.doi.org/10.1139/z04-051.
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The polytene chromosome banding pattern of Simulium exasperans (Craig, 1987) is described for the first time. Three populations of S. exasperans from Moorea and Tahiti were examined cytologically. Interspecific comparisons revealed that S. exasperans is homosequential in chromosomal banding pattern to Simulium cataractarum (Craig, 1987), but contains three species-characteristic floating inversions: IL-1ex.2ex, IIL-1ex,2ex, and IIIL-1ex. No sex-linked inversions were identified; males and females had undifferentiated sex chromosomes. The IIL-1ex,2ex inversion was in Hardy-Weinberg disequilibrium in two of the three populations. From this preliminary data, two cytotypes may exist: cytotype A (Belvedre Cascade population) and cytotype B (1st Afareaitu Cascade and Jardin Public Vaipahi populations). Contrary to phylogenetic and biogeographic data, it is hypothesized that the Belvedre Cascade population (cytotype A) is ancestral to the populations containing cytotype B. Furthermore, a heterozygote advantage may exist in cytotype B.
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Luke, S., R. S. Verma, R. A. Conte und T. Mathews. „Molecular characterization of the secondary constriction region (qh) of human chromosome 9 with pericentric inversion“. Journal of Cell Science 103, Nr. 4 (01.12.1992): 919–23. http://dx.doi.org/10.1242/jcs.103.4.919.
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Pericentric inversion of the secondary constriction region (qh) of human chromosome 9 is a frequent occurrence. This structural alteration is regarded as a normal familial variant, termed heteromorphism, and is inherited in a Mendelian fashion without any apparent phenotypic consequences. We characterized the qh region of chromosome 9 from five individuals using a series of molecular cytogenetic techniques. Four out of the five individuals have an additional area composed of alphoid DNA sequences on the inverted chromosome 9 while one case was found to have an apparently intact alphoid DNA sequence. Although the direct function(s) of alphoid DNA sequences remain unclear, the centromeric breakage involving these sequences in inverted chromosome 9 raises a series of questions pertaining to the monocentric, dicentric and pseudodicentric nature of pericentric inversions. Nevertheless, these findings have prompted us to suggest that the structural organization of alphoid DNA sequences of the centromeric region of chromosome 9 are apparently “breakage prone” and may be associated with a higher incidence of pericentric inversions. Furthermore, the hierarchical organization of various satellite DNA families (alpha-satellite, beta-satellite and satellite III) within the primary and secondary constriction regions of chromosomes 9 are elucidated here.
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Segall, A. M., und J. R. Roth. „Recombination between homologies in direct and inverse orientation in the chromosome of Salmonella: intervals which are nonpermissive for inversion formation.“ Genetics 122, Nr. 4 (01.08.1989): 737–47. http://dx.doi.org/10.1093/genetics/122.4.737.
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Abstract Sequences placed in inverse order at particular chromosome sites (permissive) recombine to generate an inversion; the same sequences, placed at other sites (nonpermissive) interact recombinationally but do not form the expected inversion recombinants. We have investigated the events that occur between sequences at nonpermissive sites. Genetically marked lac operons in inverse order were placed at nonpermissive sites in a single chromosome and Lac+ recombinants were selected. No inversions were formed. The Lac+ recombinants recovered include double-recombinant types in which information appears to have undergone a nonreciprocal information exchange; one mutant copy is repaired with no alteration of the other copy. Recombination within the lac operon is stimulated more than 100-fold by the presence of extensive homology (antenna sequences) outside of the region for which recombination is selected. Sequences placed in direct order at the ends of the same noninvertible chromosome segment recombine to form all the expected recombinant types including those in which a reciprocal exchange has generated a duplication. All the detected recombinant types can be accounted for by recombination between sister chromosomes. These results are discussed in terms of two alternative models. One explanation of the failure to detect inversion of some intervals is that particular inversions are lethal, despite the fact that no essential sequences are disrupted. Another explanation is that chromosome topology prevents sequences at nonpermissive sites in a single chromosome from engaging in the direct interaction required for inversion formation, but allows the sister strand exchanges that can generate the recombinant observed.
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Salceda, Víctor. „Geographical changes in relative frequency of inversions in chromosome III of Drosophila pseudoobscura among natural populations from Mexico“. Genetika 41, Nr. 2 (2009): 155–67. http://dx.doi.org/10.2298/gensr0902155s.
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Chromosomal polymorphism in natural populations of Drosophila pseudoobscura have been broadly studied in the USA but scarcely in Mexico where only about 60 localities have been analyzed. Differences among both regions are notorious with respect to their chromosomal constitution. Northern populations, those of USA, have as representative inversions the sequences ST, AR and CH contrasting with those in Southern populations (Mexico) in which prevail the gene arrangements TL, CU and SC. Assuming as a probable mechanism that has allowed these substitutions the flow generated by the presence of a North - South clines, we took as a goal find out if such clines really exist. With that objective in mind we studied 29 populations of this species distributed along four North - South transects. Specimens of D. pseudoobscura caught by attracting them with fermenting bananas were carried to the laboratory where from each female an isofemale line was established. When their offspring appeared a single larva from each isofemale was taken, its salivary glands extracted and stained with a solution of lacto-aceto- orcein, by these means the polytene chromosomes were obtained. On these chromosomes we identified, for each larva, the inversion (s) carried in the third chromosome, in such a way 3439 third chromosomes were analyzed. Among the 29 localities we identified 17 different inversions but the number of them varied from population to population from three to eleven. Relative frequencies of each inversion at every location were calculated and with them for each transect the presence or absence of clines was determined. Among each transect the existence of clines was observed only between two or three near by populations, but we were not able to find a clear manifestation of the presence of clines along a complete transect. Our results at this respect are similar to those previously reported for USA populations. A mechanism that explains North - South substitutions of predominant inversions remains as open question.
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Rivera, H., M. Gutiérrez-Angulo und J. R. González-Garcia. „Chromosome 9qh inversions may not be true inversions“. Human Genetics 105, Nr. 1 (1999): 181. http://dx.doi.org/10.1007/s004390051086.
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Rivera, Horacio, Melva Gutiérrez-Angulo und Juan Ramón González-Garcia. „Chromosome 9qh inversions may not be true inversions“. Human Genetics 105, Nr. 1-2 (01.07.1999): 181–82. http://dx.doi.org/10.1007/s004399900072.
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Miller, Danny E. „The Interchromosomal Effect: Different Meanings for Different Organisms“. Genetics 216, Nr. 3 (November 2020): 621–31. http://dx.doi.org/10.1534/genetics.120.303656.
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The term interchromosomal effect was originally used to describe a change in the distribution of exchange in the presence of an inversion. First characterized in the 1920s by early Drosophila researchers, it has been observed in multiple organisms. Nearly half a century later, the term began to appear in the human genetics literature to describe the hypothesis that parental chromosome differences, such as translocations or inversions, may increase the frequency of meiotic chromosome nondisjunction. Although it remains unclear if chromosome aberrations truly affect the segregation of structurally normal chromosomes in humans, the use of the term interchromosomal effect in this context persists. This article explores the history of the use of the term interchromosomal effect and discusses how chromosomes with structural aberrations are segregated during meiosis.
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Navarro, Arcadio, Esther Betrán, Carlos Zapata und Alfredo Ruiz. „Dynamics of gametic disequilibria between loci linked to chromosome inversions: the recombination-redistributing effect of inversions“. Genetical Research 67, Nr. 1 (Februar 1996): 67–76. http://dx.doi.org/10.1017/s0016672300033486.
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SummaryThe total gametic disequilibrium between two loci linked to polymorphic inversions can be partitioned into two types of components: within and between chromosome arrangements. The within components depend on the gametic disequilibrium within each chromosome arrangement. The between components depend on the locus-inversion disequilibria. This partitioning has practical applications and is indispensable for studying the dynamics of these systems because inversions greatly reduce recombination in the heterokaryotypes while allowing free, and sometimes different, recombination in each of the homokaryotypes. We provide equations for the per generation change of the various disequilibria for systems with two and three chromosome arrangements, and the general recursive equations predicting the disequilibria after any number of generations for the case of two arrangements. Simulation studies were carried out using different values of the recombination parameters and all possible initial conditions. The results show a complex convergence to linkage equilibrium in inversion systems. The various disequilibria can have local maxima and minima while approaching equilibrium and, moreover, their dynamics cannot be described, in general, using a single parameter, i.e. an effective recombination rate. We conclude that the effects of inversions on gametic disequilibria must be carefully considered when dealing with disequilibriain inversion systems. The formulae provided in this paper can be used for such purpose.
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Amores, Angel, Catherine A. Wilson, Corey A. H. Allard, H. William Detrich und John H. Postlethwait. „Cold Fusion: Massive Karyotype Evolution in the Antarctic Bullhead Notothen Notothenia coriiceps“. G3 Genes|Genomes|Genetics 7, Nr. 7 (01.07.2017): 2195–207. http://dx.doi.org/10.1534/g3.117.040063.
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Abstract Half of all vertebrate species share a series of chromosome fusions that preceded the teleost genome duplication (TGD), but we do not understand the causative evolutionary mechanisms. The “Robertsonian-translocation hypothesis” suggests a regular fusion of each ancestral acro- or telocentric chromosome to just one other by centromere fusions, thus halving the karyotype. An alternative “genome-stirring hypothesis” posits haphazard and repeated fusions, inversions, and reciprocal and nonreciprocal translocations. To study large-scale karyotype reduction, we investigated the decrease of chromosome numbers in Antarctic notothenioid fish. Most notothenioids have 24 haploid chromosomes, but bullhead notothen (Notothenia coriiceps) has 11. To understand mechanisms, we made a RAD-tag meiotic map with ∼10,000 polymorphic markers. Comparative genomics aligned about a thousand orthologs of platyfish and stickleback genes along bullhead chromosomes. Results revealed that 9 of 11 bullhead chromosomes arose by fusion of just two ancestral chromosomes and two others by fusion of three ancestral chromosomes. All markers from each ancestral chromosome remained contiguous, implying no inversions across fusion borders. Karyotype comparisons support a history of: (1) Robertsonian fusions of 22 ancestral chromosomes in pairs to yield 11 fused plus two small unfused chromosomes, like N. angustata; (2) fusion of one of the remaining two ancestral chromosomes to a preexisting fused pair, giving 12 chromosomes like N. rossii; and (3) fusion of the remaining ancestral chromosome to another fused pair, giving 11 chromosomes in N. coriiceps. These results raise the question of what selective forces promoted the systematic fusion of chromosomes in pairs and the suppression of pericentric inversions in this lineage, and provide a model for chromosome fusions in stem teleosts.
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Guijo, Maria Isabel, Josette Patte, Maria del Mar Campos, Jean-Michel Louarn und José Emilio Rebollo. „Localized Remodeling of theEscherichia coliChromosome: The Patchwork of Segments Refractory and Tolerant to Inversion Near the Replication Terminus“. Genetics 157, Nr. 4 (01.04.2001): 1413–23. http://dx.doi.org/10.1093/genetics/157.4.1413.
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AbstractThe behavior of chromosomal inversions in Escherichia coli depends upon the region they affect. Regions flanking the replication terminus have been termed nondivisible zones (NDZ) because inversions ending in the region were either deleterious or not feasible. This regional phenomenon is further analyzed here. Thirty segments distributed between 23 and 29 min on the chromosome map have been submitted to an inversion test. Twenty-five segments either became deleterious when inverted or were noninvertible, but five segments tolerated inversion. The involvement of polar replication pause sites in this distribution was investigated. The results suggest that the Tus/pause site system may forbid some inversion events, but that other constraints to inversion, unrelated to this system, exist. Our current model for deleterious inversions is that the segments involved carry polar sequences acting in concert with other polar sequences located outside the segments. The observed patchwork of refractory and tolerant segments supports the existence of several NDZs in the 23- to 29-min region. Microscopic observations revealed that deleterious inversions are associated with high frequencies of abnormal nucleoid structure and distribution. Combined with other information, the data suggest that NDZs participate in the organization of the terminal domain of the nucleoid.
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Ahearn, Jayne N., und Visut Baimai. „Cytogenetic study of three closely related species of Hawaiian Drosophila“. Genome 29, Nr. 1 (01.02.1987): 47–57. http://dx.doi.org/10.1139/g87-008.
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Three allopatric species from the Hawaiian islands, Drosophila bostrycha (Molokai), D. affinidisjuncta (West Maui), and D. disjuncta (East Maui), are extremely similar in morphology but differ in metaphase chromosomes by the amount and distribution of heterochromatin. Their polytene chromosomes are virtually homosequential with only slight differences at the tip of the microchromosome. Each is polymorphic for one or more inversions, especially in chromsome 4. Salivary gland chromosomes of F1 larvae reared either from wild-caught females or wild-caught males mated to standard laboratory stocks were examined for gene arrangements. Drosophila bostrycha and D. affinidisjuncta share a polymorphism for inversion 4v, which is much more frequent in the latter than in the former. In D. disjuncta 4v has been found only joined in a haplotype with three other inversions (g2 h2 i2) at a low frequency at Kipahulu Valley. Drosophila disjuncta is unique in having another fourth chromosome inversion, 4k, which is highest in frequency at Waikamoi. A new inversion, 2s, was discovered at Uluini Stream. Interspecific hybridizations were carried out in small mass matings. Backcrosses and dissections demonstrated that all F1 females were fertile. All F1 males were sterile in either of two categories with reciprocal hybrids uniformly manifesting one or the other type. Attempts to model the sterility mechanism suggest that more than chromosomal sterility is involved. Our results are discussed in relation to other closely related clusters of species having heterochromatin-based karyotype variations. Key words: heterochromatin, hybrid sterility, inversion, polymorphism, species divergence.
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Bedo, D. G. „A cytological study of Simulium ruficorne (Diptera: Simuliidae) and its relationship to the S. ornatipes species complex“. Genome 32, Nr. 4 (01.08.1989): 570–79. http://dx.doi.org/10.1139/g89-484.
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Polytene chromosome banding patterns in Simulium ruficorne populations from two island and a continental African locality were analyzed and a standard map was prepared. Distinct arrays of fixed and polymorphic rearrangements characterize unique cytotypes in Santiago Island, Tenerife, and Ivory Coast populations. Sex-chromosome differentiation where an inversion linked to the male determiner marks a Y chromosome also occurs in the Santiago Island population. No sibling species can be defined at present because of the absence of sympatric population samples. Comparison of banding patterns between S. ruficorne and the S. ornatipes–neornatipes species complex in Australia and New Caledonia shows striking similarities. Banding homology is readily established with about 90% of polytene banding recognizable between the two standards. Three inversions are shared between the lineages, further emphasizing their similarity. These results provide independent corroboration of the close relationship between S. ruficorne and S. ornatipes established from conventional taxonomy. The validity of using shared inversions and common breakpoints in phylogenetic comparisons is discussed in relation to the possibility of confusing similar but distinct rearrangements and the inversion-generating role of transposable elements. The possibility of transposable element mediated identical, independently derived, rearrangements seems unlikely, but in all studies the confusion of phylogenies by similar inversions must be carefully considered.Key words: Simulium ruficorne, polytene chromosome, inversion phylogeny.
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Salceda, Víctor, und José Espinoza-Velazquez. „Micro-geographic variation of inversions in natural populations of Drosophila pseudoobscura“. Genetika 38, Nr. 2 (2006): 97–105. http://dx.doi.org/10.2298/gensr0602097s.
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Chromosomal polymorphism for the third chromosome in Drosophila pseudoobscura has been widely studied for genetic variation in different environments or locations far apart. However, there is less information regarding sites geographically near one another. Targeting on possible micro-geographic variation in the species, a serial study was done on 12 Mexican populations grouped in four regions, including locations in Durango (DU), the border area of Guanajuato-San Luis Potosi states (GP), Chiapas (CH) and Saldilo (SA). Flies were trapped in their natural habitats using fermenting bananas as bait. They were individually cultivated in the laboratory for larvae production. In a given population sample several flies were cultivated together but only one larva per culture provided salivary tissue to observe polytene chromosomes. Gene arrangements or inversions were identified and frequencies were calculated. A total of 767 third chromosomes were studied and 11 different inversions detected. The type and relative frequencies of the arrangements varied among regions. From the 11 inversions observed, 10 were found in Durango, five in Guanajuato-San Luis Potosi and Chiapas, and eight in Saltillo. The inversion frequencies in the Durango locations varied in four cases, but only one in Chiapas, three cases in Guanajuato-San Luis Potosi, and five in Saltillo. It was also observed that there were geographical gradients for inversions within regions as follows: four arrangements in Saltillo and Durango, three in Guanajuato-San Luis Potos? and one in Chiapas. Moreover, all four regions studied showed evidences for micro-geographical variation. Nevertheless, more studies are needed to elucidate the relevance of the inversion frequencies changes in neighboring populations and also any seasonal-annual frequencies observed in the locations studied here.
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Caccone, Adalgisa, Gi-Sik Min und Jeffrey R. Powell. „Multiple Origins of Cytologically Identical Chromosome Inversions in the Anopheles gambiae Complex“. Genetics 150, Nr. 2 (01.10.1998): 807–14. http://dx.doi.org/10.1093/genetics/150.2.807.
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Abstract For more than 60 years, evolutionary cytogeneticists have been using naturally occurring chromosomal inversions to infer phylogenetic histories, especially in insects with polytene chromosomes. The validity of this method is predicated on the assumption that inversions arise only once in the history of a lineage, so that sharing a particular inversion implies shared common ancestry. This assumption of monophyly has been generally validated by independent data. We present the first clear evidence that naturally occurring inversions, identical at the level of light microscopic examination of polytene chromosomes, may not always be monophyletic. The evidence comes from DNA sequence analyses of regions within or very near the breakpoints of an inversion called the 2La that is found in the Anopheles gambiae complex. Two species, A. merus and A. arabiensis, which are fixed for the “same” inversion, do not cluster with each other in a phylogenetic analysis of the DNA sequences within the 2La. Rather, A. merus 2La is most closely related to strains of A. gambiae homozygous for the 2L+. A. gambiae and A. merus are sister taxa, the immediate ancestor was evidently homozygous 2L+, and A. merus became fixed for an inversion cytologically identical to that in A. arabiensis. A. gambiae is polymorphic for 2La/2L+, and the 2La in this species is nearly identical at the DNA level to that in A. arabiensis, consistent with the growing evidence that introgression has or is occurring between these two most important vectors of malaria in the world. The parallel evolution of the “same” inversion may be promoted by the presence of selectively important genes within the breakpoints.
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McKinney, Garrett, Megan V. McPhee, Carita Pascal, James E. Seeb und Lisa W. Seeb. „Network Analysis of Linkage Disequilibrium Reveals Genome Architecture in Chum Salmon“. G3: Genes|Genomes|Genetics 10, Nr. 5 (12.03.2020): 1553–61. http://dx.doi.org/10.1534/g3.119.400972.
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Many studies exclude loci that exhibit linkage disequilibrium (LD); however, high LD can signal reduced recombination around genomic features such as chromosome inversions or sex-determining regions. Chromosome inversions and sex-determining regions are often involved in adaptation, allowing for the inheritance of co-adapted gene complexes and for the resolution of sexually antagonistic selection through sex-specific partitioning of genetic variants. Genomic features such as these can escape detection when loci with LD are removed; in addition, failing to account for these features can introduce bias to analyses. We examined patterns of LD using network analysis to identify an overlapping chromosome inversion and sex-determining region in chum salmon. The signal of the inversion was strong enough to show up as false population substructure when the entire dataset was analyzed, while the effect of the sex-determining region on population structure was only obvious after restricting analysis to the sex chromosome. Understanding the extent and geographic distribution of inversions is now a critically important part of genetic analyses of natural populations. Our results highlight the importance of analyzing and understanding patterns of LD in genomic dataset and the perils of excluding or ignoring loci exhibiting LD. Blindly excluding loci in LD would have prevented detection of the sex-determining region and chromosome inversion while failing to understand the genomic features leading to high-LD could have resulted in false interpretations of population structure.