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1
Bedo, D. G. « Polytene chromosome mapping in Ceratitis capitata (Diptera : Tephritidae) ». Genome 29, no 4 (1 août 1987) : 598–611. http://dx.doi.org/10.1139/g87-101.
Texte intégralRésumé :
Polytene chromosome reference maps of the five autosomes of Ceratitis capitata from male pupal orbital bristle trichogen cells are presented and a correlation is established between two of them and the two largest of the five autosomes in the haploid mitotic complement. Characteristic features of each chromosome are described identifying areas that are difficult to analyze and noting the existence of common alternative band expression. A quantitative analysis of the mitotic karyotype of C. capitata indicates that the two smallest autosome pairs cannot be reliably distinguished. This may present problems with future attempts to establish homologies between the remaining mitotic and polytene chromosomes. A comparison of polytene chromosome banding patterns from salivary gland and trichogen cells failed to find any homologous regions, or even to identify homologous chromosomes. The banding differences are not explained by variation in puffing patterns, heterochromatin expression, or polyteny levels, but appear to reflect fundamental differences in banding patterns of the chromosomes in each tissue. Key words: Ceratitis capitata, polytene chromosome map, mitotic chromosome measurements.
2
Zacharopoulou, A. « Polytene chromosome maps in the Medfly Ceratitis capitata ». Genome 33, no 2 (1 avril 1990) : 184–97. http://dx.doi.org/10.1139/g90-030.
Texte intégralRésumé :
Polytene chromosome maps of the five autosomes from salivary gland cells in Ceratitis capitata are presented, and the more characteristic features of each element are described. The correlation of the polytene elements to miotic chromosomes and linkage groups is established by using various Y-autosome and autosome-autosome translocation lines. Two loci, dp (black pupal case) and w (white pupal case), are mapped to the third and fifth chromosome, respectively. In addition to the polytene maps presented, some extra figures of specific chromosomal regions are given for easier identification of each polytene element.Key words: polytene chromosome maps, Ceratitis capitata.
3
Garcia-Martinez, V., E. Hernandez-Ortiz, C. S. Zepeta-Cisneros, A. S. Robinson, A. Zacharopoulou et G. Franz. « Mitotic and polytene chromosome analysis in the Mexican fruit fly, Anastrepha ludens (Loew) (Diptera : Tephritidae) ». Genome 52, no 1 (janvier 2009) : 20–30. http://dx.doi.org/10.1139/g08-099.
Texte intégralRésumé :
The present study constitutes the first attempt to construct a polytene chromosome map of an Anastrepha species, Anastrepha ludens (Loew), a major agricultural pest. The mitotic karyotype has a diploid complement of 12 acrocentric chromosomes, including five pairs of autosomes and an XX/XY sex chromosome pair. The analysis of salivary gland polytene chromosomes has shown a total number of five polytene elements that correspond to the five autosomes. The characteristic features and the most prominent landmarks of each chromosome are described. By comparing chromosome banding patterns, the possible chromosomal homology between A. ludens and Ceratitis capitata (Wiedemann) is presented. This work shows that polytene maps of A. ludens are suitable for cytogenetic studies in this species and may be used as reference for other Anastrepha species, most of which are also serious agricultural pests.
4
Zhao, J. T., M. Frommer, J. A. Sved et A. Zacharopoulou. « Mitotic and polytene chromosome analyses in the Queensland fruit fly, Bactrocera tryoni (Diptera : Tephritidae) ». Genome 41, no 4 (1 août 1998) : 510–26. http://dx.doi.org/10.1139/g98-053.
Texte intégralRésumé :
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.
5
Bedo, D. G. « Polytene and mitotic chromosome analysis in Ceratitis capitata (Diptera ; Tephritidae) ». Canadian Journal of Genetics and Cytology 28, no 2 (1 avril 1986) : 180–88. http://dx.doi.org/10.1139/g86-025.
Texte intégralRésumé :
Polytene chromosomes were found in several larval and pupal tissues of the Medfly, Ceratitis capitata, during a search for chromosomes suitable for detailed cytological analysis. Well-banded highly polytene chromosomes, which could be adequately separated and spread, were found in trichogen cells of the spatulate superior orbital bristles of male pupae. These chromosomes proved suitable for full polytene analysis. Thoracic trichogen cells of both male and female pupae also contain useful polytene chromosomes, although they are considerably thinner and thus more difficult to analyze. Contrasting with those in pupal trichogen cells, the chromosomes in the salivary glands, Malphighian tubules, midgut, hindgut, and fat body of larvae and pupae were difficult to prepare because of high levels of ectopic pairing and chromosome fragmentation. In hindgut preparations partial separation of up to three chromosomes was achieved, but in all other tissues no useful chromosome separation was possible. In trichogen polytene cells, five banded chromosomes and a prominent heterochromatic network associated with a nucleolus are found. The mitotic chromosomes respond to C- and Q-banding and silver staining with considerable variation. This is especially so in the X chromosome, which displays an extensive array of bands following both Q-banding and silver staining. Comparison of Q-banded metaphase and polytene chromosomes demonstrates that the five autosomes are represented by conventional polytene chromosomes, while the sex chromosomes are contained in the heterochromatic net, most of which fluoresces strongly. This suggests that the Q-bands of the mitotic X chromosome are replicated to a greater extent than the nonfluorescent material in polytene cells. This investigation shows C. capitata to have excellent cytological material for both polytene and mitotic analysis.Key words: Ceratitis capitata, Medfly, chromosomes (polytene), banding (chromosome).
6
Bedo, D. G. « Polytene chromosomes of the Old World screwworm fly (Chrysomya bezziana) and its evolutionary relationships with Lucilia cuprina and Cochliomyia hominivorax (Diptera : Calliphoridae) ». Genome 35, no 2 (1 avril 1992) : 294–303. http://dx.doi.org/10.1139/g92-045.
Texte intégralRésumé :
Standard polytene chromosome maps for the Old World screwsworm fly, Chrysomya bezziana, are presented. Good quality polytene chromosomes obtainable from pupal trichogen cells allow detailed analysis of autosomal euchromatin. The sex chromosomes are represented by irregular heterochromatic structures resembling those described previously in trichogen polytene chromosomes of the Australian sheep blowfly, Lucilia cuprina. A high degree of homology with the banding pattern of L. cuprina polytene chromosomes allowed direct recognition of approximately 60% of the L. cuprina complement in the C. bezziana maps. A further 13% may be homologous. The extensive homology observed is discussed in relation to the rate of chromosome rearrangement and conservation of karyotype elements in the evolution of Calliphorid flies. The observed conservation in polytene banding patterns should facilitate construction of phylogenies over a number of generic groups.Key words: Chrysomya bezziana, screwworm, polytene map, chromosome homology.
7
Liang, Jiangtao, Simon M. Bondarenko, Igor V. Sharakhov et Maria V. Sharakhova. « Obtaining Polytene, Meiotic, and Mitotic Chromosomes from Mosquitoes for Cytogenetic Analysis ». Cold Spring Harbor Protocols 2022, no 12 (5 août 2022) : pdb.prot107872. http://dx.doi.org/10.1101/pdb.prot107872.
Texte intégralRésumé :
Chromosome visualization is a key step for developing cytogenetic maps and idiograms, analyzing inversion polymorphisms, and identifying mosquito species. Three types of chromosomes—polytene, mitotic, and meiotic—are used in cytogenetic studies of mosquitoes. Here, we describe a detailed method for obtaining high-quality polytene chromosome preparations from the salivary glands of larvae and the ovaries of females forAnophelesmosquitoes. We also describe how to obtain mitotic chromosomes from imaginal discs of fourth-instar larvae and meiotic chromosomes from the testes of male pupae for all mosquitoes. These chromosomes can be used for fluorescence in situ hybridization (FISH), a fundamental technique in cytogenetic research that is used for physical genome mapping, detecting chromosomal rearrangements, and studying chromosome organization.
8
Shahjahan, Reza M., et Farzana Yesmin. « Polytene chromosome maps of the melon fly Bactrocera cucurbitae (Diptera : Tephritidae) ». Genome 45, no 6 (1 décembre 2002) : 1167–74. http://dx.doi.org/10.1139/g02-081.
Texte intégralRésumé :
Standard photographic maps of the polytene chromosomes are presented for the melon fly Bactrocera cucurbitae, a serious pest of fleshy fruits and vegetables. Five larval salivary gland polytene chromosomes (10 polytene arms) were isolated, and their characteristic features and landmarks have been recognized. Banding patterns of each of the polytene arms are presented, where variation in band intensity and puffs appear to reflect fundamental differences in chromosomes. The whole polytene genome has been typically mapped by dividing it into 100 sections and the subsections were lettered. The mitotic chromosomes of larval brain ganglia are also examined, five pairs of autosomes and an XX/XY sex chromosome pair. In addition, a heterochromatic mass corresponding to the sex chromosomes are observed in the polytene nuclei of salivary gland tissue. This investigation showed that B. cucurbitae has excellent cytological material for polytene chromosome analysis and proved to be very useful for obtaining more detailed genetic information on the pest's natural populations.Key words: Bactrocera cucurbitae, salivary gland, banding patterns, polytene maps.
9
Zambetaki, Anna, Nicole Pasteur et Penelope Mavragani-Tsipidou. « Cytogenetic analysis of Malpighian tubule polytene chromosomes of Culex pipiens (Diptera : Culicidae) ». Genome 41, no 6 (1 décembre 1998) : 751–55. http://dx.doi.org/10.1139/g98-090.
Texte intégralRésumé :
A simple technique is described for obtaining well-spread and readable Malpighian tubule polytene nuclei of Culex pipiens on a routine basis. Detailed polytene chromosome maps are presented with a description of the most prominent landmarks of each chromosome, the regions with asynapsis and the most frequent weak points identified in the polytene arms. Usable Malpighian tubule polytene chromosomes should facilitate molecular cytogenetic, genetic, and potentially biosystematic studies on this medically important global vector of viral inducing encephalitis.Key words: Culex pipiens, polytene chromosomes, Malpighian tubules, banding pattern, photomap.
10
Henry, Willie, Subrata Kumar Dey, Rakesh Varma, Sachin Thapa et William S. Procunier. « Polytene chromosomes of an Indian Himalayan black fly Simulium (Nevermannia) praelargum (Diptera : Simuliidae) ». Current Zoology 56, no 4 (1 août 2010) : 437–44. http://dx.doi.org/10.1093/czoolo/56.4.437.
Texte intégralRésumé :
Abstract High quality polytene chromosome maps (n=3) of a Himalayan Simuliid Simulium praelargum Datta, 1973 are presented and represent the first cytological description of a taxon found in the feuerborni group, subgenus Nevermannia. Polytene chromosomes one (I) and two (II) are metacentric, chromosome three (III) is submetacentric with the length of each chromosome occupying 37.25 %, 31.36 % and 31.34 % of the total complement length, respectively. Typical simuliid diagnostic intergeneric chromosomal markers are found within the polytene complement of this species. The nucleolar organizer (N.O.) is found at the base of the short arm of chromosome one (IS), the Ring of Balbiani (R.B.), double bubble (D.B.) and triad occur in the short arm of chromosome two (IIS), the Parabalbiani Ring (P.B.) and grey band (gb) occur in the long arm of chromosome two (IIL) and the Blister (BL) and Capsule (Ca) occur in the short arm of chromosome three (IIIS).Terminal bands at the end of IIIS are heterochromatinized and present atypically with respect to other simuliid fauna. Populations studied so far are unique among the Simuliidae in that they exhibit chromosome structural monomorphism. These high resolution polytene chromosome maps will form the basis for future cytological characterization and phylogenetic comparisons amongst members of the feuerborni group.
11
Zambetaki, Anna, Kleanthis Kleanthous et Penelope Mavragani-Tsipidou. « Cytogenetic analysis of Malpighian tubule and salivary gland polytene chromosomes of Bactrocera oleae (Dacus oleae) (Diptera : Tephritidae) ». Genome 38, no 6 (1 décembre 1995) : 1070–81. http://dx.doi.org/10.1139/g95-143.
Texte intégralRésumé :
Photomaps of the Malpighian tubule and the salivary gland polytene chromosomes of Bactrocera oleae (Dacus oleae) are presented and compared with those of the fat body. Five polytene chromosomes (10 polytene arms) corresponding to the five autosomes of the mitotic nuclei, as well as a heterochromatic mass corresponding to the sex chromosomes, are observed in the nuclei of the three somatic tissues. The most prominent features of each polytene chromosome, the reverse tandem duplications, as well as the rather unusual ectopic pairing of the telomeric regions of different chromosome arms, are described. The constancy of the banding pattern based on the analysis of the three larval tissues is discussed.Key words: Bactrocera oleae (Dacus oleae), polytene chromosomes, salivary gland, Malpighian tubule, banding pattern.
12
Semeshin, V. F., I. F. Zhimulev, D. Kritikou et A. Zacharopoulou. « Electron microscope investigation of polytene chromosomes in the Mediterranean fruit fly Ceratitis capitata ». Genome 38, no 4 (1 août 1995) : 652–60. http://dx.doi.org/10.1139/g95-083.
Texte intégralRésumé :
Ultrastructural analyses of polytene chromosomes from male pupal orbital bristle cells and from larval salivary glands of Ceratitis capitata were carried out. It was shown that chromatin complexes corresponding to the X chromosome heterochromatic network are surrounded by material containing ribonucleoprotein (RNP) granules 250–300 Å (1 Å = 0.1 nm) in diameter. RNP granules of similar size surround the spherical Y chromosome. These data point out the presence of transcriptional activity in both of these chromosomes. The absence of clear structure in chromosomal regions situated between large bands in both types of tissues was observed. These results support the hypothesis of weak synapsis between chromatids or small chromomeres of polytene chromosomes in this species. In addition, we describe a specific puff revealed in both orbital trichogen cells and salivary glands that is morphologically similar to the 93D puff of Drosophila melanogaster.Key words: Ceratitis capitata, polytene chromosomes, electron microscopy.
13
Dej, K. J., et A. C. Spradling. « The endocycle controls nurse cell polytene chromosome structure during Drosophila oogenesis ». Development 126, no 2 (15 janvier 1999) : 293–303. http://dx.doi.org/10.1242/dev.126.2.293.
Texte intégralRésumé :
Polytene chromosomes exhibit intricate higher order chromatin structure that is easily visualized due to their precisely aligned component strands. However, it remains unclear if the same factors determine chromatin organization in polyploid and diploid cells. We have analyzed one such factor, the cell cycle, by studying changes in Drosophila nurse cell chromosomes throughout the 10 to 12 endocycles of oogenesis. We find that nurse cells undergo three distinct types of endocycle whose parameters are correlated with chromosome behavior. The first four endocycles support complete DNA replication; poorly banded polytene euchromatin progressively condenses during the late S phases to produce blob-like chromosomes. During the unique fifth endocycle, an incomplete late S phase is followed by a mitosis-like state during which the 64C chromosomes dissociate into 32 chromatid pairs held together by unreplicated regions. All the subsequent endocycles lack any late S phase; during these cycles a new polytene chromosome grows from each 2C chromatid pair to generate 32-ploid polytene nuclei. These observations suggest that euchromatin begins to condense during late S phase and that nurse cell polytene chromosome structure is controlled by regulating whether events characteristic of late S and M phase are incorporated or skipped within a given endocycle.
14
Zacharopoulou, A., K. Bourtzis et Ph Kerremans. « A comparison of polytene chromosomes in salivary glands and orbital bristle trichogen cells in Ceratitis capitata ». Genome 34, no 2 (1 avril 1991) : 215–19. http://dx.doi.org/10.1139/g91-034.
Texte intégralRésumé :
The banding patterns of polytene chromosomes in different tissues of the Mediterranean fruit fly, Ceratitis capitata, vary to such an extent that homologous chromosomes cannot be recognised. However, analyses of autosomal breakpoints in several translocation strains allowed chromosomes from the two tissues to be aligned despite their difference in banding pattern. These results were discussed, considering the different hypotheses of the origin and biological significance of polytene chromosome bands.Key words: polytene chromosomes, salivary gland chromosomes, orbital bristle trichogen cell chromosomes, Ceratitis capitata.
15
Sharakhov, Igor V., Maria V. Sharakhova, Charles M. Mbogo, Lizette L. Koekemoer et Guiyun Yan. « Linear and Spatial Organization of Polytene Chromosomes of the African Malaria Mosquito Anopheles funestus ». Genetics 159, no 1 (1 septembre 2001) : 211–18. http://dx.doi.org/10.1093/genetics/159.1.211.
Texte intégralRésumé :
Abstract Anopheles funestus Giles is one of the major malaria vectors in Africa, but little is known about its genetics. Lack of a cytogenetic map characterized by regions has hindered the progress of genetic research with this important species. This study developed a cytogenetic map of An. funestus using ovarian nurse cell polytene chromosomes. We demonstrate an important application with the cytogenetic map for characterizing various chromosomal inversions for specimens collected from coastal Kenya. The linear and spatial organization of An. funestus polytene chromosomes was compared with the best-studied malaria mosquito, An. gambiae Giles. Comparisons of chromosome morphology between the two species have revealed that the most extensive chromosomal rearrangement occurs in pericentromeric heterochromatin of autosomes. Differences in pericentromeric heterochromatin types correlate with nuclear organization differences between An. funestus and An. gambiae. Attachments of chromosomes to the nuclear envelope strongly depend on the presence of diffusive β-heterochromatin. Thus, An. funestus and An. gambiae exhibit species-specific characteristics in chromosome-linear and -spatial organizations.
16
Gariou-Papalexiou, A., G. Yannopoulos, A. Zacharopoulou et R. H. Gooding. « Photographic polytene chromosome maps for Glossina morsitans submorsitans (Diptera : Glossinidae) : cytogenetic analysis of a colony with sex-ratio distortion ». Genome 45, no 5 (1 octobre 2002) : 871–80. http://dx.doi.org/10.1139/g02-057.
Texte intégralRésumé :
Photographic polytene chromosome maps from trichogen cells of pharate adult Glossina morsitans submorsitans were constructed. Using the standard system employed to map polytene chromosomes of Drosophila, the characteristic landmarks were described for the X chromosome and the two autosomes (L1 and L2). Sex-ratio distortion, which is expressed in male G. m. submorsitans, was found to be associated with an X chromosome (XB) that contains three inversions in each arm. Preliminary data indicate no differences in the fecundity of XAXA and XAXB females, but there are indications that G. m. submorsitans in colonies originating from Burkina Faso and Nigeria have genes on the autosomes and (or) the Y chromosome that suppress expression of sex-ratio distortion.Key words: tsetse, Glossina morsitans submorsitans, polytene chromosome maps, inversions, sex-ratio distortion.
17
Chaudhry, S., Neetu, S. Gupta et J. S. Chhilar. « Salivary polytene chromosome mapping of Anopheles (Cellia) subpictus Grassi (Culicidae : Diptera) ». Genome 48, no 2 (1 avril 2005) : 241–46. http://dx.doi.org/10.1139/g04-120.
Texte intégralRésumé :
With the introduction of molecular taxonomy of mosquitoes, polytene chromosome maps have become indispensable as standard references for locating genes, puffs, and inversion breakpoints of unique DNA sequences. We present a line map and a photomap of the salivary polytene chromosomes of Anopheles (Cellia) subpictus Grassi, an important emerging vector of malaria in India. In addition, we discuss the nature of this species complex consisting of sibling species A, B, C, and D. The comparative study is in relevance to the X chromosome heterozygous inversion differences between 2 allopatric populations of the species and the recognition of 4 X-chromosome inversion genotypes viz: species A–X+a+b, B–Xab, C–Xa+b and D–X+ab.Key words: Anopheles subpictus, polytene chromosome map.
18
Khoroshko, Varvara A., Galina V. Pokholkova, Victor G. Levitsky, Tatyana Yu Zykova, Oksana V. Antonenko, Elena S. Belyaeva et Igor F. Zhimulev. « Genes Containing Long Introns Occupy Series of Bands and Interbands in Drosophila melanogaster Polytene Chromosomes ». Genes 11, no 4 (11 avril 2020) : 417. http://dx.doi.org/10.3390/genes11040417.
Texte intégralRésumé :
The Drosophila melanogaster polytene chromosomes are the best model for studying the genome organization during interphase. Despite of the long-term studies available on genetic organization of polytene chromosome bands and interbands, little is known regarding long gene location on chromosomes. To analyze it, we used bioinformatic approaches and characterized genome-wide distribution of introns in gene bodies and in different chromatin states, and using fluorescent in situ hybridization we juxtaposed them with the chromosome structures. Short introns up to 2 kb in length are located in the bodies of housekeeping genes (grey bands or lazurite chromatin). In the group of 70 longest genes in the Drosophila genome, 95% of total gene length accrues to introns. The mapping of the 15 long genes showed that they could occupy extended sections of polytene chromosomes containing band and interband series, with promoters located in the interband fragments (aquamarine chromatin). Introns (malachite and ruby chromatin) in polytene chromosomes form independent bands, which can contain either both introns and exons or intron material only. Thus, a novel type of the gene arrangement in polytene chromosomes was discovered; peculiarities of such genetic organization are discussed.
19
Sukowati, S., et V. Baimai. « A standard cytogenetic map for Anopheles sundaicus (Diptera : Culicidae) and evidence for chromosomal differentiation in populations from Thailand and Indonesia ». Genome 39, no 1 (1 février 1996) : 165–73. http://dx.doi.org/10.1139/g96-022.
Texte intégralRésumé :
A standard photographic map of polytene chromosomes of Anopheles sundaicus was constructed from ovarian nurse cells and is described herein. Polytene chromosomes of wild specimens collected from 9 different geographical areas in Thailand and Indonesia have been analyzed. Specimens from these populations appear to share banding patterns with standard gene arrangements, except for some specimens from Purworejo, in Central Java, and South Tapanuli and Asahan, both of North Sumatra, which exhibited distinct banding patterns at the tip of chromosome X (Xb) compared with the standard sequence (Xa). Moreover, some specimens collected from Asahan, North Sumatra, consistently showed distinct loosely diffuse bands in zone 19 of chromosome arm 2R (2Rb) compared with the standard banding patterns (2Ra). The existence of the 2Rb pattern correlates perfectly with the presence of an extra block of centromeric heterochromatin in autosome 2 as revealed by mitotic karyotype analysis (2n = 6). These cytological differences have led to the recognition of 3 distinct forms, viz., A, B, and C, within the taxon An. sundaicus. In addition, forms A and C show a normal size for chromosome Y, (Y1), while form B has a relatively larger type of chromosome Y, (Y2). Form A is widely distributed in Thailand and Indonesia, while form B has been found in North Sumatra and Central Java. Form C, however, has been found only in Asahan, North Sumatra. Key words : Anopheles sundaicus, polytene chromosome map, mitotic karyotype, chromosomal differentiation.
20
Perez, Alba Moncada, et Jan Conn. « A polytene chromosome study of four populations of Anopheles aquasalis from Venezuela ». Genome 35, no 2 (1 avril 1992) : 327–31. http://dx.doi.org/10.1139/g92-049.
Texte intégralRésumé :
Polytene chromosome studies were undertaken to elucidate taxonomic relationships among populations of Anopheles aquasalis and A. emilianus in Venezuela. Four collection sites were chosen: two in Sucre state (Santa Fe and Guayana) where A. aquasalis (considered to be A. emilianus by Gabaldón and Escalante) is presumed to be the major regional vector of Plasmodium vivax; and two in areas where no malaria transmission occurs (Caño Rico, Aragua state, and Puerto Cabello, Carabobo state). The chromosome banding pattern of the four populations was identical and conformed to the standard chromosome map of A. aquasalis from Brazil. These results suggest that the population from Santa Fe and Guayana, considered to be A. emilianus, is conspecific with A. aquasalis. However, its status as a distinct species with a homosequential polytene chromosome banding pattern cannot be ruled out.Key words: polytene chromosomes, Anopheles aquasalis, malaria, chromosome banding.
21
Hunter, Fiona F. « The polytene chromosomes of Simulium furculatum (Shewell) (Diptera : Simuliidae) ». Genome 32, no 4 (1 août 1989) : 522–30. http://dx.doi.org/10.1139/g89-478.
Texte intégralRésumé :
To test whether Simulium furculatum (Shewell) belongs to the Simulium vernum (Macquart) species-group, a comparison was made of the polytene chromosomes of S. furculatum and the S. vernum "Knebworth" standard. Only two chromosome arms (of six) could be completely analysed. It is argued that S. furculatum does not belong to the S. vernum species-group. A complex sex-chromosome system (X1, X2, Y1) is found in both eastern and western Canada. Phylogenetically, the single Y chromosome is intermediate between the two X chromosomes. Intraspecific inversion polymorphisms, which serve to differentiate eastern from western populations, are also identified. Only one sibling is indicated.Key words: black flies, Simulium furculatum, Simulium vernum, cytotaxonomy, polytene chromosomes, sex chromosomes.
22
Zacharopoulou, A., M. E. Riva, A. Malacrida et G. Gasperi. « Cytogenetic characterization of a genetic sexing strain in Ceratitis capitata ». Genome 34, no 4 (1 août 1991) : 606–11. http://dx.doi.org/10.1139/g91-092.
Texte intégralRésumé :
A genetic sexing strain of Ceratitis capitata, carrying a null mutation for ADH activity linked to the Y chromosome, was analysed cytogenetically. In addition to an insertion of a large part of the Y chromosome into chromosome 2, this strain carries two other chromosomal rearrangements, a deletion in the second chromosome and a reciprocal translocation involving chromosomes 2 and 4. The progeny of the T(2;4) translocation heterozygote with unbalanced chromosome constitution can survive up to the larval and (or) to the adult stage. These cytological characteristics are discussed in relation to the genetic sexing behaviour of this line.Key words: Ceratitis capitata, polytene chromosomes, genetic sexing.
23
Kuvangkadilok, Chaliow, Suwannee Phayuhasena et Visut Baimai. « Population cytogenetic studies on Simulium feuerborni Edwards (Diptera : Simuliidae) from northern Thailand ». Genome 42, no 1 (1 février 1999) : 80–86. http://dx.doi.org/10.1139/g98-106.
Texte intégralRésumé :
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
24
Kounatidis, Ilias, Nikolaos Papadopoulos, Kostas Bourtzis et Penelope Mavragani-Tsipidou. « Genetic and cytogenetic analysis of the fruit fly Rhagoletis cerasi (Diptera : Tephritidae) ». Genome 51, no 7 (juillet 2008) : 479–91. http://dx.doi.org/10.1139/g08-032.
Texte intégralRésumé :
The European cherry fruit fly, Rhagoletis cerasi , is a major agricultural pest for which biological, genetic, and cytogenetic information is limited. We report here a cytogenetic analysis of 4 natural Greek populations of R. cerasi, all of them infected with the endosymbiotic bacterium Wolbachia pipientis . The mitotic karyotype and detailed photographic maps of the salivary gland polytene chromosomes of this pest species are presented here. The mitotic metaphase complement consists of 6 pairs of chromosomes, including one pair of heteromorphic sex chromosomes, with the male being the heterogametic sex. The analysis of the salivary gland polytene complement has shown a total of 5 long chromosomes (10 polytene arms) that correspond to the 5 autosomes of the mitotic nuclei and a heterochromatic mass corresponding to the sex chromosomes. The most prominent landmarks of each polytene chromosome, the “weak points”, and the unusual asynapsis of homologous pairs of polytene chromosomes at certain regions of the polytene elements are also presented and discussed.
25
Bedo, D. G. « Nucleolar fragmentation in polytene trichogen cells of Lucilia cuprina and Chrysomya bezziana (Diptera : Calliphoridae) ». Genome 35, no 2 (1 avril 1992) : 283–93. http://dx.doi.org/10.1139/g92-044.
Texte intégralRésumé :
The location of genes coding for 18S and 28S ribosomal RNA in mitotic and polytene cells of Lucilia cuprina and Chrysomya bezziana was investigated using in situ hybridization of an 18 + 28S ribosomal gene probe and silver staining. In both species ribosomal genes were localized to secondary constriction regions in sex chromosome heterochromatin. In L. cuprina mitotic cells the probe hybridizes to a distal secondary constriction region in the short arms of the X and Y chromosomes. In C. bezziana mitotic chromosomes ribosomal genes were located in distal secondary constriction regions in the long arms of the X and Y chromosomes. In polytene trichogen cells of both species, hybridization results varied with the level of polyteny. Cells of low polyteny have a single hybridization site, but with greater polytenization, increasing numbers of extrachromosomal fragments strongly hybridize to the ribosomal gene probe. No hybridization occurs in structures representing the sex chromosomes or in the autosomes. These results indicate that fragmentation and dispersal of the nucleolus occurs during polytenization. Silver staining of both unsquashed and squashed polytene nuclei show identical behaviour of multiple, varied-sized nucleolar bodies, thus confirming the in situ hybridization results. Uridine incorporation studies in L. cuprina indicate that transcription occurs in extrachromosomal bodies similar to nucleolar fragments. Nucleolar fragmentation is more pronounced in L. cuprina males, particularly in those with the translocation T(Y;2)540. Chromosomally normal C. bezziana show nucleolar fragmentation levels similar to that in L. cuprina males. Ribosomal genes are disproportionately replicated in trichogen cells to a much greater extent than surrounding heterochromatin. Nucleolar fragmentation may be a gene amplification system, but it is not known to what degree, relative to diploid amounts, ribosomal genes replicate in trichogen cells.Key words: Lucilia cuprina, Chrysomya bezziana, polytene cells, ribosomal genes, nucleolar fragmentation, disproportionate replication, heterochromatin.
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Drosopoulou, Elena, Ifigeneia Nakou et Penelope Mavragani-Tsipidou. « The Bactrocera oleae genome : localization of nine genes on the polytene chromosomes of the olive fruit fly (Diptera : Tephritidae) ». Genome 57, no 10 (octobre 2014) : 573–76. http://dx.doi.org/10.1139/gen-2014-0172.
Texte intégralRésumé :
Four homologous and five heterologous gene-specific sequences have been mapped by in situ hybridization on the salivary gland polytene chromosomes of the olive fruit fly, Bactrocera oleae. The nine genes were dispersed on four of the five autosomal chromosomes, thus enriching the available set of chromosome landmarks for this major agricultural pest. Present data further supports the proposed chromosome homologies among B. oleae, Ceratitis capitata, and Drosophila melanogaster and the idea of the conservation of chromosomal element identity throughout dipteran evolution.
27
Poopittayasataporn, Anan, et Visut Baimai. « Polytene chromosome relationships of five species of the Anopheles dirus complex in Thailand ». Genome 38, no 3 (1 juin 1995) : 426–34. http://dx.doi.org/10.1139/g95-056.
Texte intégralRésumé :
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.
28
Chaudhry, Asha, Preety Bhinder, Ram Kumar et Ravneet Kaur. « Evaluation of the mutagenic potential of propoxur and methyl parathion using polytene chromosomes of Anopheles stephensi ». Journal of Applied and Natural Science 4, no 1 (1 juin 2012) : 79–84. http://dx.doi.org/10.31018/jans.v4i1.227.
Texte intégralRésumé :
The mutagenicity of two pesticides, propoxur and methyl parathion was evaluated by using polytene chromosomes of Anopheles stephensi. The results were based on the frequency of various structural aberrations encountered in the polytene chromosomes of the larvae treated with LC20 of propoxur and methyl parathion separately. Propoxur induced a total of 67 aberrations as against 15 in the controls while methyl parathion induced 53 aberrations as against 13 in the controls. These aberrations were dominated by inversions, translocations, deletions, ectopic pairing, asynapses, breaks, fusions and induced puffing. The frequency of propoxur induced aberrations was highest in chromosome 3R followed by 2R, 3L, 2L and X-chromosome. Methyl parathion induced highest number of aberrations in 2R followed by 2L, 3R, 3L and X-chromosomes. This study suggests that larval polytene chromosomes are sensitive indicators of pesticide genotoxicity in which both propoxur and methyl parathion are significantly chromotoxic for the genome of a mosquito taken as an experimental insect.
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Cai, H., P. Kiefel, J. Yee et I. Duncan. « A yeast artificial chromosome clone map of the Drosophila genome. » Genetics 136, no 4 (1 avril 1994) : 1385–99. http://dx.doi.org/10.1093/genetics/136.4.1385.
Texte intégralRésumé :
Abstract We describe the mapping of 979 randomly selected large yeast artificial chromosome (YAC) clones of Drosophila DNA by in situ hybridization to polytene chromosomes. Eight hundred and fifty-five of the clones are euchromatic and have primary hybridization sites in the banded portions of the polytene chromosomes, whereas 124 are heterochromatic and label the chromocenter. The average euchromatic clone contains about 211 kb and, at its primary site, labels eight or nine contiguous polytene bands. Thus, the extent as well as chromosomal position of each clone has been determined. By direct band counts, we estimate our clones provide about 76% coverage of the euchromatin of the major autosomes, and 63% coverage of the X. When previously reported YAC mapping data are combined with ours, euchromatic coverage is extended to about 90% for the autosomes and 82% for the X. The distribution of gap sizes in our map and the coverage achieved are in good agreement with expectations based on the assumption of random coverage, indicating that euchromatic clones are essentially randomly distributed. However, certain gaps in coverage, including the entire fourth chromosome euchromatin, may be significant. Heterochromatic sequences are underrepresented among the YAC clones by two to three fold. This may result, at least in part, from underrepresentation of heterochromatic sequences in adult DNA (the source of most of the clones analyzed), or from clone instability.
30
George, Phillip, Nicholas A. Kinney, Jiangtao Liang, Alexey V. Onufriev et Igor V. Sharakhov. « Three-dimensional Organization of Polytene Chromosomes in Somatic and Germline Tissues of Malaria Mosquitoes ». Cells 9, no 2 (1 février 2020) : 339. http://dx.doi.org/10.3390/cells9020339.
Texte intégralRésumé :
Spatial organization of chromosome territories and interactions between interphase chromosomes themselves, as well as with the nuclear periphery, play important roles in epigenetic regulation of the genome function. However, the interplay between inter-chromosomal contacts and chromosome-nuclear envelope attachments in an organism’s development is not well-understood. To address this question, we conducted microscopic analyses of the three-dimensional chromosome organization in malaria mosquitoes. We employed multi-colored oligonucleotide painting probes, spaced 1 Mb apart along the euchromatin, to quantitatively study chromosome territories in larval salivary gland cells and adult ovarian nurse cells of Anopheles gambiae, An. coluzzii, and An. merus. We found that the X chromosome territory has a significantly smaller volume and is more compact than the autosomal arm territories. The number of inter-chromosomal, and the percentage of the chromosome–nuclear envelope, contacts were conserved among the species within the same cell type. However, the percentage of chromosome regions located at the nuclear periphery was typically higher, while the number of inter-chromosomal contacts was lower, in salivary gland cells than in ovarian nurse cells. The inverse correlation was considerably stronger for the autosomes. Consistent with previous theoretical arguments, our data indicate that, at the genome-wide level, there is an inverse relationship between chromosome-nuclear envelope attachments and chromosome–chromosome interactions, which is a key feature of the cell type-specific nuclear architecture.
31
Kaiser, P. E., J. A. Seawright et B. K. Birky. « Chromosome polymorphism in natural populations of Anopheles quadrimaculatus Say species A and B ». Genome 30, no 2 (1 avril 1988) : 138–46. http://dx.doi.org/10.1139/g88-024.
Texte intégralRésumé :
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.
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Brockhouse, Charles, J. A. B. Bass, R. M. Feraday et N. A. Straus. « Supernumerary chromosome evolution in the Simulium vernum group (Diptera : Simuliidae) ». Genome 32, no 4 (1 août 1989) : 516–21. http://dx.doi.org/10.1139/g89-477.
Texte intégralRésumé :
B chromosomes are present in a cluster of closely related species of black fly in the Simulium vernum group including six sibling species within the S. vernum complex, Simulium costatum, and Simulium juxtacrenobium. The S. vernum siblings all possess the same small metacentric supernumerary, while S. juxtacrenobium carries three different supernumeraries (two telocentrics and one metacentric) and S. costatum has both a metacentric and a telocentric B chromosome. Analysis of the polytene chromosomes in the larval salivary glands has revealed relationships between the supernumeraries of the different species. The metacentric B chromosome of the S. vernum siblings apparently results from a fusion of the two telocentric supernumeraries of S. juxtacrenobium. Acquisition of a nucleolar organizer then gave rise to the metacentric B chromosome in S. juxtacrenobium. The acquisition of a nucleolus by a S. juxtacrenobium telocentric gave rise to one of the S. costatum supernumeraries. Two alternate models for the origin of black fly supernumeraries are presented.Key words: supernumerary chromosome, black fly, polytene chromosome, chromosome evolution.
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Schmiemann, Manfred G., et Michael M. Bentley1. « In vitro analyses of cuticular differentiation at the chromosomal level in Lucilia sericata ». Genome 30, no 4 (1 août 1988) : 603–7. http://dx.doi.org/10.1139/g88-101.
Texte intégralRésumé :
The large bristles of flies sclerotize and melanize during the pupal phase well before the rest of the cuticle. Each bristle is the product of two cells, the trichogen cell and the tormogen cell. Both their nuclei exhibit analyzable polytene chromosomes. The pupal metathoracic integument of Lucilia sericata has been excised and cultivated in Schneider's Drosophila medium for extended periods of time. Among the differentiations taking place in vitro, the most obvious is the stiffening and coloring of the bristles. The in vitro differentiation very much resembles the in vivo differentiation in its timing and appearance. Explants excised early in pupal development cannot differentiate in vitro, while those excised and cultured at later stages can. Actinomycin D was administered to the culture medium and the incorporation of [3H]uridine was analyzed after long incubations to determine if this process was a reaction of dead cuticle or controlled by living cells. The analysis of chromosome structure and puffing patterns in the five polytene chromosomes of the trichogen cell after in vitro cultivation shows that transcriptional activity is not dependent on the existence of normal chromosome conformation. The degree of pycnotic reaction and puff induction of the nuclei, however, varied under different culture conditions. The capacity of this system for differentiation can be used to study in vitro chromosomal activity during the course of development.Key words: in vitro, polytene chromosomes, sclerotization, cuticle.
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Leach, Thomas J., Heather L. Chotkowski, Michael G. Wotring, Robert L. Dilwith et Robert L. Glaser. « Replication of Heterochromatin and Structure of Polytene Chromosomes ». Molecular and Cellular Biology 20, no 17 (1 septembre 2000) : 6308–16. http://dx.doi.org/10.1128/mcb.20.17.6308-6316.2000.
Texte intégralRésumé :
ABSTRACT Heterochromatin is characteristically the last portion of the genome to be replicated. In polytene cells, heterochromatic sequences are underreplicated because S phase ends before replication of heterochromatin is completed. Truncated heterochromatic DNAs have been identified in polytene cells of Drosophila and may be the discontinuous molecules that form between fully replicated euchromatic and underreplicated heterochromatic regions of the chromosome. In this report, we characterize the temporal pattern of heterochromatic DNA truncation during development of polytene cells. Underreplication occurred during the first polytene S phase, yet DNA truncation, which was found within heterochromatic sequences of all fourDrosophila chromosomes, did not occur until the second polytene S phase. DNA truncation was correlated with underreplication, since increasing the replication of satellite sequences with thecycE 1672 mutation caused decreased production of truncated DNAs. Finally, truncation of heterochromatic DNAs was neither quantitatively nor qualitatively affected by modifiers of position effect variegation including the Y chromosome,Su(var)2052 , parental origin, or temperature. We propose that heterochromatic satellite sequences present a barrier to DNA replication and that replication forks that transiently stall at such barriers in late S phase of diploid cells are left unresolved in the shortened S phase of polytene cells. DNA truncation then occurs in the second polytene S phase, when new replication forks extend to the position of forks left unresolved in the first polytene S phase.
35
Mavragani-Tsipidou, P., G. Karamanlidou, A. Zacharopoulou, S. Koliais et C. Kastritsis. « Mitotic and polytene chromosome analysis in Dacus oleae (Diptera : Tephritidae) ». Genome 35, no 3 (1 juin 1992) : 373–78. http://dx.doi.org/10.1139/g92-056.
Texte intégralRésumé :
The present study constitutes the first attempt to construct a photographic map of the polytene chromosomes of Dacus oleae, a pest of the olive tree that causes serious financial damage in all olive oil producing countries. The map was constructed by using the larval fat body cells, the chromosomes of which are representative of the polytene chromosomes of other polytene tissues. In addition, the mitotic chromosomes of brain ganglia were examined, permitting tentative correlations between mitotic and polytene elements. This investigation shows that D. oleae is suitable for cytogenetic analysis in both mitotic and polytene chromosomes, a fact that may prove very useful for obtaining more detailed genetic information on the pest's natural populations.Key words: Dacus oleae, polytene chromosomes, mitotic chromosomes.
36
Sidorenko, D. S., T. Yu Zykova, V. A. Khoroshko, G. V. Pokholkova, S. A. Demakov, J. Larsson, E. S. Belyaeva et I. F. Zhimulev. « Polytene chromosomes reflect functional organization of the Drosophila genome ». Vavilov Journal of Genetics and Breeding 23, no 2 (30 mars 2019) : 148–53. http://dx.doi.org/10.18699/vj19.474.
Texte intégralRésumé :
Polytene chromosomes of Drosophila melanogaster are a convenient model for studying interphase chromosomes of eukaryotes. They are giant in size in comparison with diploid cell chromosomes and have a pattern of cross stripes resulting from the ordered chromatid arrangement. Each region of polytene chromosomes has a unique banding pattern. Using the model of four chromatin types that reveals domains of varying compaction degrees, we were able to correlate the physical and cytological maps of some polytene chromosome regions and to show the main properties of genetic and molecular organization of bands and interbands, that we describe in this review. On the molecular map of the genome, the interbands correspond to decompacted aquamarine chromatin and 5’ ends of ubiquitously active genes. Gray bands contain lazurite and malachite chromatin, intermediate in the level of compaction, and, mainly, coding parts of genes. Dense black transcriptionally inactive bands are enriched in ruby chromatin. Localization of several dozens of interbands on the genome molecular map allowed us to study in detail their architecture according to the data of whole genome projects. The distribution of proteins and regulatory elements of the genome in the promoter regions of genes localized in the interbands shows that these parts of interbands are probably responsible for the formation of open chromatin that is visualized in polytene chromosomes as interbands. Thus, the permanent genetic activity of interbands and gray bands and the inactivity of genes in black bands are the basis of the universal banding pattern in the chromosomes of all Drosophila tissues. The smallest fourth chromosome of Drosophila with an atypical protein composition of chromatin is a special case. Using the model of four chromatin states and fluorescent in situ hybridization, its cytological map was refined and the genomic coordinates of all bands and interbands were determined. It was shown that, in spite of the peculiarities of this chromosome, its band organization in general corresponds to the rest of the genome. Extremely long genes of different Drosophila chromosomes do not fit the common scheme, since they can occupy a series of alternating bands and interbands (up to nine chromosomal structures) formed by parts of these genes.
37
Staiber, W. « Unusual germ line limited chromosomes in Acricotopus lucidus (Diptera, Chironomidae) ». Genome 29, no 5 (1 octobre 1987) : 702–5. http://dx.doi.org/10.1139/g87-120.
Texte intégralRésumé :
A small supernumerary polytene chromosome was found during the last 8 years in some rare cases in larval salivary gland cells of Acricotopus lucidus (Diptera, Chironomidae). The chromosome may be derived from the germ line restricted parts of the genome. It consists of a short heterochromatic segment and of euchromatic sections with banding patterns homologous to sections of the short arm of soma chromosome I. When examining male meiosis, an exceptional small germ line limited chromosome was found. It is believed that this chromosome was not always recognized during soma elimination as a germ line limited chromosome, probably because of its partial homology to one of the soma chromosomes, and was then polytenized in salivary gland cells. Another germ line limited chromosome with a characteristic morphology and with a special behavior in differential gonial mitosis was found to have existed for more than 12 years in a laboratory stock. In differential gonial mitosis this special germ line limited chromosome partly pairs with the long arm of soma chromosome I. The present results strongly support the idea that the germ line limited chromosomes of A. lucidus are derived from the soma chromosomes, and show that chromosomes of the germ line restricted part of the genome can persist for many generations in a laboratory stock in spite of complex chromosome elimination mechanisms in the primary germ cells. Key words: germ line limited chromosomes, supernumerary polytene chromosome, salivary gland, Acricotopus lucidus.
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Kolesnikova, Tatyana D., Alexandra V. Kolodyazhnaya, Galina V. Pokholkova, Veit Schubert, Viktoria V. Dovgan, Svetlana A. Romanenko, Dmitry Yu Prokopov et Igor F. Zhimulev. « Effects of Mutations in the Drosophila melanogaster Rif1 Gene on the Replication and Underreplication of Pericentromeric Heterochromatin in Salivary Gland Polytene Chromosomes ». Cells 9, no 6 (19 juin 2020) : 1501. http://dx.doi.org/10.3390/cells9061501.
Texte intégralRésumé :
In Drosophila salivary gland polytene chromosomes, a substantial portion of heterochromatin is underreplicated. The combination of mutations SuURES and Su(var)3-906 results in the polytenization of a substantial fraction of unique and moderately repeated sequences but has almost no effect on satellite DNA replication. The Rap1 interacting factor 1 (Rif) protein is a conserved regulator of replication timing, and in Drosophila, it affects underreplication in polytene chromosomes. We compared the morphology of pericentromeric regions and labeling patterns of in situ hybridization of heterochromatin-specific DNA probes between wild-type salivary gland polytene chromosomes and the chromosomes of Rif1 mutants and SuUR Su(var)3-906 double mutants. We show that, despite general similarities, heterochromatin zones exist that are polytenized only in the Rif1 mutants, and that there are zones that are under specific control of Su(var)3-9. In the Rif1 mutants, we found additional polytenization of the largest blocks of satellite DNA (in particular, satellite 1.688 of chromosome X and simple satellites in chromosomes X and 4) as well as partial polytenization of chromosome Y. Data on pulsed incorporation of 5-ethynyl-2′-deoxyuridine (EdU) into polytene chromosomes indicated that in the Rif1 mutants, just as in the wild type, most of the heterochromatin becomes replicated during the late S phase. Nevertheless, a significantly increased number of heterochromatin replicons was noted. These results suggest that Rif1 regulates the activation probability of heterochromatic origins in the satellite DNA region.
39
Conn, Jan. « A cytogenetic analysis of the polytene chromosomes of Anopheles triannulatus (Diptera : Culicidae) from western Venezuela ». Genome 34, no 2 (1 avril 1991) : 267–72. http://dx.doi.org/10.1139/g91-042.
Texte intégralRésumé :
The larval polytene chromosomes of Anopheles triannulatus are described for the first time in this report. The population from western Venezuela was chosen arbitrarily as the chromosome standard and is the basis for the photomap presented here. Anopheles triannulatus displays whole-arm associations distinct from other members of the subgenus Nyssorhynchus that have been examined cytogenetically. The association pattern for An. triannulatus is 2R–3R and 2L–3L, rather than the more common 2R–2L and 3R–3L. The possible role of whole-arm translocations in speciation is briefly discussed.Key words: Anopheles triannulatus, polytene chromosome photomap, whole-arm translocation, Venezuela.
40
Ramírez, Corália CL, et Eliana MB Dessen. « Chromosomal evidence for sibling species of the malaria vector Anopheles cruzii ». Genome 43, no 1 (1 février 2000) : 143–51. http://dx.doi.org/10.1139/g99-103.
Texte intégralRésumé :
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.
41
Vieira, Jorge, Cristina P. Vieira, Daniel L. Hartl et Elena R. Lozovskaya. « Discordant Rates of Chromosome Evolution in the Drosophila virilis Species Group ». Genetics 147, no 1 (1 septembre 1997) : 223–30. http://dx.doi.org/10.1093/genetics/147.1.223.
Texte intégralRésumé :
Abstract In Drosophila, the availability of polytene chromosome maps and of sets of probes covering most regions of the chromosomes allows a direct comparison of the organization of the genome in different species. In this work, we report the localization, in Drosophila virilis, D. montana, and D. novamexicana, of >100 bacteriophage P1 clones containing ~65 kilobase inserts of genomic DNA from D. virilis. Each clone hybridizes with a single euchromatic site in either chromosome 1 or chromosome 3 in D. virilis. From these data, it is possible to estimate the minimum number of inversions required to transform the map positions of the probes in one species into the map positions of the same probes in a related species. The data indicate that, in the D. virilis species group, the X chromosome has up to four times the number of inversions as are observed in chromosome 3. The first photographic polytene chromosome maps for D. montana and D. novamexicana are also presented.
42
Soboleva, Evgenia S., Kirill M. Kirilenko, Valentina S. Fedorova, Alina A. Kokhanenko, Gleb N. Artemov et Igor V. Sharakhov. « Two Nested Inversions in the X Chromosome Differentiate the Dominant Malaria Vectors in Europe, Anopheles atroparvus and Anopheles messeae ». Insects 15, no 5 (26 avril 2024) : 312. http://dx.doi.org/10.3390/insects15050312.
Texte intégralRésumé :
The Maculipennis subgroup of malaria mosquitoes includes both dominant malaria vectors and non-vectors in Eurasia. Understanding the genetic factors, particularly chromosomal inversions, that differentiate Anopheles species can provide valuable insights for vector control strategies. Although autosomal inversions between the species in this subgroup have been characterized based on the chromosomal banding patterns, the number and positions of rearrangements in the X chromosome remain unclear due to the divergent banding patterns. Here, we identified two large X chromosomal inversions, approximately 13 Mb and 10 Mb in size, using fluorescence in situ hybridization. The inversion breakpoint regions were mapped by hybridizing 53 gene markers with polytene chromosomes of An. messeae. The DNA probes were designed based on gene sequences from the annotated An. atroparvus genome. The two nested inversions resulted in five syntenic blocks. Only two small syntenic blocks, which encompass 181 annotated genes in the An. atroparvus genome, changed their position and orientation in the X chromosome. The analysis of the An. atroparvus genome revealed an enrichment of gene ontology terms associated with immune system and mating behavior in the rearranged syntenic blocks. Additionally, the enrichment of DNA transposons was found in sequences homologous to three of the four breakpoint regions. This study demonstrates the successful application of the physical genome mapping approach to identify rearrangements that differentiate species in insects with polytene chromosomes.
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Artemov, Gleb, Vladimir Stegniy, Maria Sharakhova et Igor Sharakhov. « The Development of Cytogenetic Maps for Malaria Mosquitoes ». Insects 9, no 3 (17 septembre 2018) : 121. http://dx.doi.org/10.3390/insects9030121.
Texte intégralRésumé :
Anopheline mosquitoes are important vectors of human malaria. Next-generation sequencing opens new opportunities for studies of mosquito genomes to uncover the genetic basis of a Plasmodium transmission. Physical mapping of genome sequences to polytene chromosomes significantly improves reference assemblies. High-resolution cytogenetic maps are essential for anchoring genome sequences to chromosomes as well as for studying breakpoints of chromosome rearrangements and chromatin protein localization. Here we describe a detailed pipeline for the development of high-resolution cytogenetic maps using polytene chromosomes of malaria mosquitoes. We apply this workflow to the refinement of the cytogenetic map developed for Anopheles beklemishevi.
44
Baimai, V., A. Poopittayasataporn et U. Kijchalao. « Cytological differences and chromosomal rearrangements in four members of the Anopheles dirus complex (Diptera : Culicidae) ». Genome 30, no 3 (1 juin 1988) : 372–79. http://dx.doi.org/10.1139/g88-065.
Texte intégralRésumé :
A reference photomap of the larval salivary gland, polytene chromosomes of the Anopheles dims complex (species A) is presented. Samples of species A, B, C, and D from natural populations in Thailand were compared to this standard map using the larval progeny of wild-caught females. All species show differences in their chromosome banding patterns involving band size, number, and shape, particularly at the free ends of the X, 2R, and 2L. These differences provide useful diagnostic characters for separating members of the species complex. However, overall banding patterns are conservative in the group: species A, B, and C are virtually homosequential. Species D is highly polymorphic for a single paracentric inversion in each of the four autosomal arms and has a fixed inversion on the X chromosome. This same X chromosome inversion occurs at low frequency in species A.Key words: Anopheles dirus, larval polytene chromosome, inversion polymorphisms.
45
Locke, John, Lynn Podemski, Nicole Aippersbach, Hilary Kemp et Ross Hodgetts. « A Physical Map of the Polytenized Region (101EF–102F) of Chromosome 4 in Drosophila melanogaster ». Genetics 155, no 3 (1 juillet 2000) : 1175–83. http://dx.doi.org/10.1093/genetics/155.3.1175.
Texte intégralRésumé :
Abstract Chromosome 4, the smallest autosome (~5 Mb in length) in Drosophila melanogaster contains two major regions. The centromeric domain (~4 Mb) is heterochromatic and consists primarily of short, satellite repeats. The remaining ~1.2 Mb, which constitutes the banded region (101E–102F) on salivary gland polytene chromosomes and contains the identified genes, is the region mapped in this study. Chromosome walking was hindered by the abundance of moderately repeated sequences dispersed along the chromosome, so we used many entry points to recover overlapping cosmid and BAC clones. In situ hybridization of probes from the two ends of the map to polytene chromosomes confirmed that the cloned region had spanned the 101E–102F interval. Our BAC clones comprised three contigs; one gap was positioned distally in 102EF and the other was located proximally at 102B. Twenty-three genes, representing about half of our revised estimate of the total number of genes on chromosome 4, were positioned on the BAC contigs. A minimal tiling set of the clones we have mapped will facilitate both the assembly of the DNA sequence of the chromosome and a functional analysis of its genes.
46
Belyaeva, E. S., L. V. Boldyreva, E. I. Volkova, R. A. Nanayev, A. A. Alekseyenko et I. F. Zhimulev. « Effect of the Suppressor of Underreplication (SuUR) Gene on Position-Effect Variegation Silencing in Drosophila melanogaster ». Genetics 165, no 3 (1 novembre 2003) : 1209–20. http://dx.doi.org/10.1093/genetics/165.3.1209.
Texte intégralRésumé :
Abstract It has been previously shown that the SuUR gene encodes a protein located in intercalary and pericentromeric heterochromatin in Drosophila melanogaster polytene chromosomes. The SuUR mutation suppresses the formation of ectopic contacts and DNA underreplication in polytene chromosomes; SuUR+ in extra doses enhances the expression of these characters. This study demonstrates that heterochromatin-dependent PEV silencing is also influenced by SuUR. The SuUR protein localizes to chromosome regions compacted as a result of PEV; the SuUR mutation suppresses DNA underreplication arising in regions of polytene chromosomes undergoing PEV. The SuUR mutation also suppresses variegation of both adult morphological characters and chromatin compaction observed in rearranged chromosomes. In contrast, SuUR+ in extra doses and its overexpression enhance variegation. Thus, SuUR affects PEV silencing in a dose-dependent manner. However, its effect is expressed weaker than that of the strong modifier Su(var)2-5.
47
Mahesh, G., N. B. Ramachandra et H. A. Ranganath. « Autoradiographic study of transcription and dosage compensation in the sex and neo-sex chromosome of Drosophila nasuta nasuta and Drosophila nasuta albomicans ». Genome 44, no 1 (1 février 2001) : 71–78. http://dx.doi.org/10.1139/g00-100.
Texte intégralRésumé :
Cellular autoradiography is used to study the transcription patterns of the polytene X chromosomes in Drosophila nasuta nasuta and D. n. albomicans. D. n. nasuta, with 2n = 8, includes a pair of complete heteromorphic sex chromosomes, whereas D. n. albomicans, with 2n = 6, has a pair of metacentric neo-sex chromosomes representing incomplete heteromorphic sex chromosomes. The neo-X chromosome has two euchromatic arms, one representing the ancestral X while the other represents the ancestral autosome 3 chromosomes. The metacentric neo-Y chromosome has one arm with a complete heterochromatic ancestral Y and the other arm with a euchromatic ancestral autosome 3. The transcription study has revealed that the X chromosome in D. n. nasuta is hyperactive, suggesting complete dosage compensation, while in the neo-X chromosome of D. n. albomicans the ancestral X chromosome is hyperactive and the ancestral autosome 3, which is part of the neo-sex chromosome, is similar to any other autosomes. This finding shows dosage compensation on one arm (XLx/) of the neo-X chromosome, while the other arm (XR3/YR3) is not dosage compensated and has yet to acquire the dosage compensatory mechanism.Key words: Drosophila, chromosomal races, neo-sex chromosome, transcription and dosage compensation.
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Bachtrog, Doris, et Brian Charlesworth. « On the Genomic Location of theexuperantia1Gene inDrosophila miranda : The Limits ofin SituHybridization Experiments ». Genetics 164, no 3 (1 juillet 2003) : 1237–40. http://dx.doi.org/10.1093/genetics/164.3.1237.
Texte intégralRésumé :
AbstractIn situ hybridization to Drosophila polytene chromosomes is a powerful tool for determining the chromosomal location of genes. Using in situ hybridization experiments, Yi and Charlesworth recently reported the transposition of the exuperantia1 gene (exu1) from a neo-sex chromosome to the ancestral X chromosome of Drosophila miranda, close to exuperantia2 (exu2). By characterizing sequences flanking exu1, however, we found the position of exu1 to be conserved on the neo-sex chromosome. Further, the exu2 gene was found to be tandemly duplicated on the X chromosome of D. miranda. The misleading hybridization signal of exu1 may be caused by multiple copies of exu2, which interfere with the hybridization of the exu1 probe to its genomic position on the neo-X chromosome. This suggests that flanking DNA should be used to confirm the positions of members of gene families.
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HAMADA, NEUSA, ELENY DA SILVA PEREIRA et PETER H. ADLER. « Polytene chromosomes of Simulium (Psaroniocompsa) daltanhani (Diptera : Simuliidae) from Central Amazonia, Brazil ». Zootaxa 1676, no 1 (9 janvier 2008) : 57. http://dx.doi.org/10.11646/zootaxa.1676.1.6.
Texte intégralRésumé :
Last-instar larvae of Simulium (Psaroniocompsa) daltanhani Hamada and Adler from a stream in Central Amazonia were analyzed cytologically by mapping their polytene chromosomes. Simulium daltanhani has the nucleolar organizer in the short arm of chromosome I, heterogametic females, and an absence of autosomal polymorphisms. The chromosomes carry multiple rearrangements relative to other analyzed members of the S. quadrifidum species group in the subgenus Psaroniocompsa. One-third of the chromosomal complement is rearranged relative to the sequence of S. ulyssesi, the species with the most similar banding pattern among studied members of the S. quadrifidum group.
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Tudor, Mark, Andrew Mitchelson et Kevin O'hare. « A 1·5 kb direct repeat sequence flanks the suppressor of forked gene at the euchromatin–heterochromatin boundary of the Drosophila melanogaster X chromosome ». Genetical Research 68, no 3 (décembre 1996) : 191–202. http://dx.doi.org/10.1017/s0016672300034169.
Texte intégralRésumé :
SummaryA 1·5 kilobasepair repeated DNA sequence is duplicated in direct orientation so as to flank the suppressor of forked gene in the euchromatin–heterochromatin transition region on the X chromosome of Drosophila melanogaster. These two copies are almost identical, but DNA blotting, analysis of cloned sequences and database searches show that elsewhere in the genome, homologous sequences are poorly conserved. They are often associated with other repeats, suggesting that they may belong to a scrambled and clustered middle repetitive DNA family. The sequences do not appear to be related to transposable elements and their location in different strains is conserved. In situ hybridization to metaphase chromosomes shows that homologous sequences are concentrated in the pericentric regions of the autosomes and the X chromosome. The sequences are not significantly under-represented in DNA from polytene tissue and must lie in the replicated regions of polytene chromosomes. The almost perfect conservation of the two repeats around suppressor of forked in D. melanogaster suggests they arose by duplication or gene conversion. Suppression of recombination in this chromosomal region presumably allows this unusual organization to be stably maintained. In the X-ray induced allele, suppressor of forked-L26, the sequence between the repeats, including the gene, and one copy of the repeat have been deleted.