scholarly journals MITOTIC RECOMBINATION IN THE HETEROCHROMATIN OF THE SEX CHROMOSOMES OF DROSOPHILA MELANOGASTER

Genetics ◽  
1978 ◽  
Vol 90 (1) ◽  
pp. 93-104
Author(s):  
P Ripoll ◽  
A Garcia-Bellido
Keyword(s):  
Drosophila Melanogaster ◽  
Y Chromosome ◽  
Sex Chromosomes ◽  
Mitotic Recombination ◽  
X Chromosomes ◽  
X Ray ◽  
Y Chromosomes ◽  
Chromosome Arm

ABSTRACT The frequency of spontaneous and X-ray-induced mitotic recombination involving the Y chromosome has been studied in individuals with a marked Y chromosome arm and different XY compound chromosomes. The genotypes used include X chromosomes with different amounts of X heterochromatin and either or both arms of the Y chromosome attached to either side of the centromere. Individuals with two Y chromosomes have also been studied. The results show that the bulk of mitotic recombination takes place between homologous regions.

scholarly journals Structural changes following the reversal of a Y Chromosome to an autosome in Drosophila pseudoobscura

2016 ◽  
Author(s):  
Ching-Ho Chang ◽  
Amanda M. Larracuente
Keyword(s):  
Y Chromosome ◽  
Single Molecule ◽  
Sex Chromosomes ◽  
Structural Changes ◽  
Drosophila Pseudoobscura ◽  
X Chromosomes ◽  
Repeat Content ◽  
Y Chromosomes ◽  
Rapid Sequence ◽  
Compact Size

AbstractRobertsonian translocations resulting in fusions between sex chromosomes and autosomes shape karyotype evolution in animals by creating new sex chromosomes from autosomes. These translocations can also reverse sex chromosomes back into autosomes, which is especially intriguing given that autosomes and sex chromosomes differ in gene regulation and chromatin environment. While researchers are beginning to understand X chromosomes reversals to autosomes at a genomic level, it is difficult to study reversals of Y chromosomes because of their rapid sequence turnover and high repeat content. To gain insight into the genomic events following a Y chromosome reversal, we investigated an autosome-Y translocation in a well-studied and tractable organism, Drosophila pseudoobscura. About 10-15 Mya, the ancestral Y chromosome fused to a small autosome (the dot chromosome) in an ancestor of D. pseudoobscura. We used single molecule real-time sequencing reads to assemble the genic part of the D. pseudoobscura dot chromosome, including this Y-to-dot translocation. We find that the intervening sequence between the ancestral Y and the rest of the dot chromosome is only ~78 Kb and has a low repeat density, suggesting that the centromere now falls outside, rather than between, the fused chromosomes. The Y-to-dot region is 100 times smaller than the D. melanogaster Y chromosome, owing to repeat landscape changes. Previous studies suggest that recurrent selective sweeps favoring shorter introns helped to shrink the Y-to-dot following the translocation. Our results suggest that genetic drift and a small ancestral Y chromosome may also help explain the compact size of the Y-to-dot translocation.

ANALYSIS OF Y-LINKED MUTATIONS TO MALE STERILITY IN DROSOPHILA MELANOGASTER

Genetics ◽  
1983 ◽  
Vol 103 (2) ◽  
pp. 219-234
Author(s):  
James A Kennison
Keyword(s):  
Drosophila Melanogaster ◽  
Y Chromosome ◽  
X Chromosome ◽  
Sex Chromosomes ◽  
Ethyl Methanesulfonate ◽  
Γ Irradiation ◽  
Y Chromosomes ◽  
Adult Feeding ◽  
Radiation Induced ◽  
Normal Spermatogenesis

ABSTRACT The frequencies of newly induced male-sterilizing lesions on both the X and Y chromosomes of Drosophila melanogaster were determined after either 4000 r of γ-irradiation or adult feeding of ethyl methanesulfonate. The Y chromosome is approximately twice as sensitive as the X chromosome to newly induced male-sterilizing lesions after γ-irradiation, but slightly less sensitive after ethyl methanesulfonate treatment. A large proportion of the radiation-induced lesions are associated with Y-autosome or X-autosome translocations, with the Y chromosome recovered in translocations far in excess of the frequency expected from metaphase lengths. Although translocations between the X and Y chromosomes or between autosomes do not appear to sterilize heterozygous males, interchanges between sex chromosomes and autosomes often sterilize males carrying them in a dominant manner, suggesting that the organization of the genome is critical for normal spermatogenesis. Complementation tests between recessive Y-linked male-sterilizing mutants do not reveal the existence of any additional fertility loci beyond the six previously defined.

scholarly journals MAGNIFICATION OF THE RIBOSOMAL GENES IN FEMALE DROSOPHILA MELANOGASTER

Genetics ◽  
1986 ◽  
Vol 114 (3) ◽  
pp. 859-874
Author(s):  
Donald J Komma ◽  
Sharyn A Endow
Keyword(s):  
Drosophila Melanogaster ◽  
Y Chromosome ◽  
Ribosomal Genes ◽  
Chromosome X ◽  
X Chromosomes ◽  
Y Chromosomes

ABSTRACT The genetically induced increase in the number of 18S + 28S ribosomal genes known as magnification has been reported to occur in male Drososphila but has not previously been observed in females. We now report that bobbed magnified (bbm) is recovered in progeny of female Drosophila carrying three different X bobbed (Xbb) chromosomes and the helper (see PDF) chromosome, which is a derivative of the Ybb- chromosome. Using different combinations of bb or bb+ X and Y chromosomes, we show that magnification in females requires both a deficiency in ribosomal genes and the presence of a Y chromosome: X/X females that are rDNA-deficient but do not carry a Y chromosome do not produce bbm; similarly, X/X/Y females that carry a Y chromosome but are not rDNA-deficient do not produce bbm. Bobbed magnified is only recovered from rDNA-deficient (see PDF), X/X/Y or (see PDF) females. We have also found that females carrying a ring Xbb chromosome together with the (see PDF) chromosome do not produce bbm, indicating that ring X chromosomes are inhibited to magnify in females as in males. We postulate that the requirement for a Y chromosome is due to sequences on the Y chromosome that regulate or encode factor(s) required for magnification, or, alternatively, affect pairing of the ribosomal genes.—These studies demonstrate that magnification is not limited to males but also occurs in females. Magnification in females is induced by rDNA-deficient conditions and the presence of a Y chromosome, and probably occurs by a mechanism similar to that in males.

scholarly journals Telomere-to-telomere assembly of a fish Y chromosome reveals the origin of a young sex chromosome pair

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Lingzhan Xue ◽  
Yu Gao ◽  
Meiying Wu ◽  
Tian Tian ◽  
Haiping Fan ◽  
...  
Keyword(s):  
Y Chromosome ◽  
Sex Chromosomes ◽  
Chromosome Pair ◽  
Sex Chromosome ◽  
Structural Variations ◽  
Recombination Suppression ◽  
Chromosome Differentiation ◽  
Y Chromosomes ◽  
Recent Origin ◽  
Mastacembelus Armatus

Abstract Background The origin of sex chromosomes requires the establishment of recombination suppression between the proto-sex chromosomes. In many fish species, the sex chromosome pair is homomorphic with a recent origin, providing species for studying how and why recombination suppression evolved in the initial stages of sex chromosome differentiation, but this requires accurate sequence assembly of the X and Y (or Z and W) chromosomes, which may be difficult if they are recently diverged. Results Here we produce a haplotype-resolved genome assembly of zig-zag eel (Mastacembelus armatus), an aquaculture fish, at the chromosomal scale. The diploid assembly is nearly gap-free, and in most chromosomes, we resolve the centromeric and subtelomeric heterochromatic sequences. In particular, the Y chromosome, including its highly repetitive short arm, has zero gaps. Using resequencing data, we identify a ~7 Mb fully sex-linked region (SLR), spanning the sex chromosome centromere and almost entirely embedded in the pericentromeric heterochromatin. The SLRs on the X and Y chromosomes are almost identical in sequence and gene content, but both are repetitive and heterochromatic, consistent with zero or low recombination. We further identify an HMG-domain containing gene HMGN6 in the SLR as a candidate sex-determining gene that is expressed at the onset of testis development. Conclusions Our study supports the idea that preexisting regions of low recombination, such as pericentromeric regions, can give rise to SLR in the absence of structural variations between the proto-sex chromosomes.

scholarly journals THE GENETICS OF A SMALL AUTOSOMAL REGION OF DROSOPHILA MELANOGASTER, INCLUDING THE STRUCTURAL GENE FOR ALCOHOL DEHYDROGENASE. V. CHARACTERIZATION OF X-RAY-INDUCED Adh NULL MUTATIONS

Genetics ◽  
1982 ◽  
Vol 102 (3) ◽  
pp. 421-435
Author(s):  
M Ashburner ◽  
C S Aaron ◽  
S Tsubota
Keyword(s):  
Drosophila Melanogaster ◽  
Alcohol Dehydrogenase ◽  
Structural Gene ◽  
End Points ◽  
X Ray ◽  
Autosomal Region ◽  
Nonrandom Distribution ◽  
Chromosome Arm ◽  
Break Points

ABSTRACT Of 31 X-ray-induced and 2 spontaneous Adh null mutations selected for resistance to pentenol (Aaron 1979), 21 are deletions, including Adh and one or more neighboring loci. By contrast, none of 13 EMS-induced Adhn mutations are deletions. On average, the size of these X-ray-induced deletions is shorter than that of 12 formaldehyde-induced Adhn deletions (O'Donnell, Mandell, Krauss and Sofer 1977). Both the X-ray- and formaldehyde-induced deletions show a nonrandom distribution of break points in region 34D to 35D of chromosome arm 2L. Some of the deletions display particular genetic properties associated with one of their end points.

Polymorphism and differentiation of rainbow trout Y chromosomes

Genome ◽  
2004 ◽  
Vol 47 (6) ◽  
pp. 1105-1113 ◽  
Author(s):  
Alicia Felip ◽  
Atushi Fujiwara ◽  
William P Young ◽  
Paul A Wheeler ◽  
Marc Noakes ◽  
...  
Keyword(s):  
Rainbow Trout ◽  
Y Chromosome ◽  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Morphological Differentiation ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
Y Chromosomes ◽  
Cytogenetic Analyses ◽  
Clonal Lines ◽  
Sex Locus

Most fish species show little morphological differentiation in the sex chromosomes. We have coupled molecular and cytogenetic analyses to characterize the male-determining region of the rainbow trout (Oncorhynchus mykiss) Y chromosome. Four genetically diverse male clonal lines of this species were used for genetic and physical mapping of regions in the vicinity of the sex locus. Five markers were genetically mapped to the Y chromosome in these male lines, indicating that the sex locus was located on the same linkage group in each of the lines. We also confirmed the presence of a Y chromosome morphological polymorphism among these lines, with the Y chromosomes from two of the lines having the more common heteromorphic Y chromosome and two of the lines having Y chromosomes morphologically similar to the X chromosome. The fluorescence in situ hybridization (FISH) pattern of two probes linked to sex suggested that the sex locus is physically located on the long arm of the Y chromosome. Fishes appear to be an excellent group of organisms for studying sex chromosome evolution and differentiation in vertebrates because they show considerable variability in the mechanisms and (or) patterns involved in sex determination.Key words: sex chromosomes, sex markers, cytogenetics, rainbow trout, fish.

DIFFERENTIAL DNA REPLICATION IN THE XX AND XY CELLS OF MUSCA DOMESTICA L. OCRA STRAIN

1970 ◽  
Vol 12 (3) ◽  
pp. 461-473 ◽  
Author(s):  
K. Y. Jan ◽  
J. W. Boyes
Keyword(s):  
Dna Replication ◽  
Musca Domestica ◽  
Sex Chromosomes ◽  
Chromosome Length ◽  
Final Part ◽  
X Chromosomes ◽  
Y Chromosomes ◽  
Heteromorphic Sex Chromosomes ◽  
Autosomal Pair ◽  
Differential Dna Replication

The karyotype of Musca domestica L. ocra strain, consists of the sex chromosomes and five autosomal pairs. The heteromorphic sex chromosomes are heterochromatic and mitotically unpaired, whereas the autosomes are euchromatic and mitotically paired. All autosomal pairs and both X and Y chromosomes are cytologically recognizable.The relative labelling rate, R (in terms of the number of grains counted per 100 labelled metaphases per μ of chromosome length) for the sex chromosomes and for each autosomal pair was followed from 1.5 hours to 8 hours after H3TdR injection. The pattern of labelling rate was similar for the different autosomal pairs in the XX cells but this pattern for the autosomal pairs in the XY cells, though also similar for the different pairs, differed appreciably from that found in the XX cells. The pattern of the labelling rate for the X chromosomes was similar in the XX and XY cells. Also the pattern of labelling rate for the X and Y chromosomes was similar during the final part of the replication period. The two X chromosomes in the XX cells and the X and Y chromosomes in the XY cells completed labelling later than the autosomes.

scholarly journals Extreme heterogeneity in sex chromosome differentiation and dosage compensation in livebearers

2019 ◽  
Vol 116 (38) ◽  
pp. 19031-19036 ◽  
Author(s):  
Iulia Darolti ◽  
Alison E. Wright ◽  
Benjamin A. Sandkam ◽  
Jake Morris ◽  
Natasha I. Bloch ◽  
...  
Keyword(s):  
Y Chromosome ◽  
Dosage Compensation ◽  
Sex Chromosomes ◽  
Poecilia Reticulata ◽  
Sex Chromosome ◽  
Sequencing Data ◽  
Chromosome Differentiation ◽  
Y Chromosomes ◽  
Shared Ancestry ◽  
Suppressed Recombination

Once recombination is halted between the X and Y chromosomes, sex chromosomes begin to differentiate and transition to heteromorphism. While there is a remarkable variation across clades in the degree of sex chromosome divergence, far less is known about the variation in sex chromosome differentiation within clades. Here, we combined whole-genome and transcriptome sequencing data to characterize the structure and conservation of sex chromosome systems across Poeciliidae, the livebearing clade that includes guppies. We found that the Poecilia reticulata XY system is much older than previously thought, being shared not only with its sister species, Poecilia wingei, but also with Poecilia picta, which diverged roughly 20 million years ago. Despite the shared ancestry, we uncovered an extreme heterogeneity across these species in the proportion of the sex chromosome with suppressed recombination, and the degree of Y chromosome decay. The sex chromosomes in P. reticulata and P. wingei are largely homomorphic, with recombination in the former persisting over a substantial fraction. However, the sex chromosomes in P. picta are completely nonrecombining and strikingly heteromorphic. Remarkably, the profound degradation of the ancestral Y chromosome in P. picta is counterbalanced by the evolution of functional chromosome-wide dosage compensation in this species, which has not been previously observed in teleost fish. Our results offer important insight into the initial stages of sex chromosome evolution and dosage compensation.

Y chromosome specific markers and the evolution of dioecy in the genus Silene

Genome ◽  
1998 ◽  
Vol 41 (2) ◽  
pp. 141-147 ◽  
Author(s):  
Y Hi Zhang ◽  
Veronica S Stilio ◽  
Farah Rehman ◽  
Amy Avery ◽  
David Mulcahy ◽  
...  
Keyword(s):  
Y Chromosome ◽  
Sex Chromosomes ◽  
Silene Latifolia ◽  
Dioecious Species ◽  
Sequence Characterized Amplified Region ◽  
Y Chromosomes ◽  
Heteromorphic Sex Chromosomes ◽  
Males And Females ◽  
Genus Silene ◽  
Evolution Of Dioecy

Sex determination in plants has been most thoroughly investigated in Silene latifolia, a dioecious species possessing heteromorphic sex chromosomes. We have identified several new Y chromosome linked RAPD markers and converted these to more reliable sequence characterized amplified region (SCAR) markers by cloning the RAPD fragments and developing longer primers. Of the primer pairs for seven SCARs, five amplify a single, unique fragment from the DNA of male S. latifolia. Two sets of primers also amplify additional fragments common to males and females. Homology between the X and Y chromosomes is sufficient to allow the amplification of fragments from females under less stringent PCR conditions. Five of the SCARs also distinguish between the sexes of closely related dioecious taxa of the section Elisanthe, but not between the sexes of distantly related dioecious species. These markers will be useful for continued investigations into the evolution of sex, phylogenetic relationships among taxa, and population dynamics of sex ratios in the genus Silene.Key words: Melandrium, RAPDs, sex chromosomes, SCARs.

Chromosomal homology of wood bison and plains bison

1977 ◽  
Vol 55 (10) ◽  
pp. 1759-1762 ◽  
Author(s):  
K. L. Ying ◽  
D. G. Peden
Keyword(s):  
Y Chromosome ◽  
Sex Chromosomes ◽  
Bison Bison ◽  
Banding Patterns ◽  
X Chromosomes ◽  
Chromosomal Homology ◽  
Wood Bison

Karyotypes of wood bison (Bison bison athabascae) and plains bison (Bison bison bison) were studied. Both subspecies were characterized by the same number of chromosomes (2n = 60), acrocentric autosomes, submetacentric X chromosomes, and an acrocentric Y chromosome. G-banding patterns suggest that when comparing wood bison and plains bison, 20 pair plus the sex chromosomes are homologous. Whether or not the remaining nine pair of chromosomes are homologous remains unknown.

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