Mammalian sex chromosomes. VI. Synapsis in the heterochromatin-rich X chromosomes of four rodent species, Mus dunni, Bandicota bengalensis, Mesocricetus auratus, and Nesokia indica

Genome ◽  
1993 ◽  
Vol 36 (1) ◽  
pp. 195-198 ◽  
Author(s):  
Amar Pal Singh ◽  
Rajiva Raman
Keyword(s):  
Sex Chromosomes ◽  
Mesocricetus Auratus ◽  
Rodent Species ◽  
Female Meiosis ◽  
X Chromosomes ◽  
Bandicota Bengalensis ◽  
Almost All

This study analyzes the progression of chromosomal synapsis in female meiosis of four rodent species, Mus dunni, Bandicota bengalensis, Mesocricetus auratus, and Nesokia indica. Special attention has been paid to understand the mode of pairing between heterochromatin-rich X chromosomes. The ovaries were obtained from newborn individuals instead of fetuses. In all but M. auratus, day 0 ovaries provided almost all the prophase stages at varying frequencies. In B. bengalensis and M. dunni the entire X chromosomes were paired including the heterochromatin. In M. auratus and N. indica, the heterochromatic arms in a proportion of X bivalents, however, were only partially synapsed. It appears that in these two species heterochromatin association is either delayed or short lived.Key words: sex chromosomes, meiosis, heterochromatin, synapsis.

scholarly journals Bisection of the X chromosome disrupts the initiation of chromosome silencing during meiosis in Caenorhabditis elegans

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yisrael Rappaport ◽  
Hanna Achache ◽  
Roni Falk ◽  
Omer Murik ◽  
Oren Ram ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Rna Polymerase Ii ◽  
X Chromosome ◽  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Transcription Analysis ◽  
X Chromosomes ◽  
Unique Character ◽  
Active Transcription ◽  
Heterogametic Sex

AbstractDuring meiosis, gene expression is silenced in aberrantly unsynapsed chromatin and in heterogametic sex chromosomes. Initiation of sex chromosome silencing is disrupted in meiocytes with sex chromosome-autosome translocations. To determine whether this is due to aberrant synapsis or loss of continuity of sex chromosomes, we engineered Caenorhabditis elegans nematodes with non-translocated, bisected X chromosomes. In early meiocytes of mutant males and hermaphrodites, X segments are enriched with euchromatin assembly markers and active RNA polymerase II staining, indicating active transcription. Analysis of RNA-seq data showed that genes from the X chromosome are upregulated in gonads of mutant worms. Contrary to previous models, which predicted that any unsynapsed chromatin is silenced during meiosis, our data indicate that unsynapsed X segments are transcribed. Therefore, our results suggest that sex chromosome chromatin has a unique character that facilitates its meiotic expression when its continuity is lost, regardless of whether or not it is synapsed.

scholarly journals Cytogenetic Analysis of the Asian Box Turtles of the Genus Cuora (Testudines, Geoemydidae)

Genes ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 156
Author(s):  
Lorenzo Clemente ◽  
Sofia Mazzoleni ◽  
Eleonora Pensabene ◽  
Tomáš Protiva ◽  
Philipp Wagner ◽  
...  
Keyword(s):  
Sex Determination ◽  
Sex Chromosomes ◽  
Wide Distribution ◽  
Iucn Red List ◽  
Telomeric Repeats ◽  
Rdna Loci ◽  
Box Turtles ◽  
Genotypic Sex Determination ◽  
Poorly Differentiated ◽  
Almost All

The Asian box turtle genus Cuora currently comprises 13 species with a wide distribution in Southeast Asia, including China and the islands of Indonesia and Philippines. The populations of these species are rapidly declining due to human pressure, including pollution, habitat loss, and harvesting for food consumption. Notably, the IUCN Red List identifies almost all species of the genus Cuora as Endangered (EN) or Critically Endangered (CR). In this study, we explore the karyotypes of 10 Cuora species with conventional (Giemsa staining, C-banding, karyogram reconstruction) and molecular cytogenetic methods (in situ hybridization with probes for rDNA loci and telomeric repeats). Our study reveals a diploid chromosome number of 2n = 52 chromosomes in all studied species, with karyotypes of similar chromosomal morphology. In all examined species, rDNA loci are detected at a single medium-sized chromosome pair and the telomeric repeats are restricted to the expected terminal position across all chromosomes. In contrast to a previous report, sex chromosomes are neither detected in Cuoragalbinifrons nor in any other species. Therefore, we assume that these turtles have either environmental sex determination or genotypic sex determination with poorly differentiated sex chromosomes. The conservation of genome organization could explain the numerous observed cases of interspecific hybridization both within the genus Cuora and across geoemydid turtles.

scholarly journals Localization of Male-Specifically Expressed MROS Genes of Silene latifolia by PCR on Flow-Sorted Sex Chromosomes and Autosomes

Genetics ◽  
2001 ◽  
Vol 158 (3) ◽  
pp. 1269-1277
Author(s):  
Eduard Kejnovský ◽  
Jan Vrána ◽  
Sachihiro Matsunaga ◽  
Přemysl Souček ◽  
Jiří Široký ◽  
...  
Keyword(s):  
Sex Chromosomes ◽  
Silene Latifolia ◽  
Homology Search ◽  
X Chromosomes ◽  
Dioecious Plants ◽  
Flow Sorting ◽  
Heteromorphic Sex Chromosomes ◽  
Copy Gene ◽  
Melandrium Album ◽  
Pcr Products

Abstract The dioecious white campion Silene latifolia (syn. Melandrium album) has heteromorphic sex chromosomes, XX in females and XY in males, that are larger than the autosomes and enable their separation by flow sorting. The group of MROS genes, the first male-specifically expressed genes in dioecious plants, was recently identified in S. latifolia. To localize the MROS genes, we used the flow-sorted X chromosomes and autosomes as a template for PCR with internal primers. Our results indicate that the MROS3 gene is located in at least two copies tandemly arranged on the X chromosome with additional copy(ies) on the autosome(s), while MROS1, MROS2, and MROS4 are exclusively autosomal. The specificity of PCR products was checked by digestion with a restriction enzyme or reamplification using nested primers. Homology search of databases has shown the presence of five MROS3 homologues in A. thaliana, four of them arranged in two tandems, each consisting of two copies. We conclude that MROS3 is a low-copy gene family, connected with the proper pollen development, which is present not only in dioecious but also in other dicot plant species.

In the platypus a meiotic chain of ten sex chromosomes shares genes with the bird Z and mammal X chromosomes

Nature ◽  
2004 ◽  
Vol 432 (7019) ◽  
pp. 913-917 ◽  
Author(s):  
Frank Grützner ◽  
Willem Rens ◽  
Enkhjargal Tsend-Ayush ◽  
Nisrine El-Mogharbel ◽  
Patricia C. M. O'Brien ◽  
...  
Keyword(s):  
Sex Chromosomes ◽  
X Chromosomes

scholarly journals Contingency in the convergent evolution of a regulatory network: Dosage compensation in Drosophila

2018 ◽  
Author(s):  
Doris Bachtrog ◽  
Chris Ellison
Keyword(s):  
Transposable Element ◽  
Dosage Compensation ◽  
Sex Chromosomes ◽  
Binding Sites ◽  
Evolutionary Biology ◽  
De Novo ◽  
Binding Motif ◽  
Sequence Motif ◽  
X Chromosomes ◽  
Msl Complex

The repeatability or predictability of evolution is a central question in evolutionary biology, and most often addressed in experimental evolution studies. Here, we infer how genetically heterogeneous natural systems acquire the same molecular changes, to address how genomic background affects adaptation in natural populations. In particular, we take advantage of independently formed neo-sex chromosomes in Drosophila species that have evolved dosage compensation by co-opting the dosage compensation (MSL) complex, to study the mutational paths that have led to the acquisition of 100s of novel binding sites for the MSL complex in different species. This complex recognizes a conserved 21-bp GA-rich sequence motif that is enriched on the X chromosome, and newly formed X chromosomes recruit the MSL complex by de novo acquisition of this binding motif. We identify recently formed sex chromosomes in the Drosophila repleta and robusta species groups by genome sequencing, and generate genomic occupancy maps of the MSL complex to infer the location of novel binding sites. We find that diverse mutational paths were utilized in each species to evolve 100s of de novo binding motifs along the neo-X, including expansions of microsatellites and transposable element insertions. However, the propensity to utilize a particular mutational path differs between independently formed X chromosomes, and appears to be contingent on genomic properties of that species, such as simple repeat or transposable element density. This establishes the “genomic environment” as an important determinant in predicting the outcome of evolutionary adaptations.

scholarly journals A Syntenic Region Conserved from Fish to Mammalian X Chromosome

2014 ◽  
Vol 2014 ◽  
pp. 1-10
Author(s):  
Guijun Guan ◽  
Meisheng Yi ◽  
Tohru Kobayashi ◽  
Yunhan Hong ◽  
Yoshitaka Nagahama
Keyword(s):  
X Chromosome ◽  
Sex Chromosomes ◽  
Random Amplified Polymorphic Dna ◽  
Comparative Genomic ◽  
X Chromosomes ◽  
Ancestral Origin ◽  
Dna Contents ◽  
Determining Factors ◽  
Unpaired Region ◽  
Syntenic Segment

Sex chromosomes bearing the sex-determining gene initiate development along the male or female pathway, no matter which sex is determined by XY male or ZW female heterogamety. Sex chromosomes originate from ancient autosomes but evolved rapidly after the acquisition of sex-determining factors which are highly divergent between species. In the heterogametic male system (XY system), the X chromosome is relatively evolutionary silent and maintains most of its ancestral genes, in contrast to its Y counterpart that has evolved rapidly and degenerated. Sex in a teleost fish, the Nile tilapia (Oreochromis niloticus), is determined genetically via an XY system, in which an unpaired region is present in the largest chromosome pair. We defined the differences in DNA contents present in this chromosome with a two-color comparative genomic hybridization (CGH) and the random amplified polymorphic DNA (RAPD) approach in XY males. We further identified a syntenic segment within this region that is well conserved in several teleosts. Through comparative genome analysis, this syntenic segment was also shown to be present in mammalian X chromosomes, suggesting a common ancestral origin of vertebrate sex chromosomes.

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 Studies on Metatherian Sex Chromosomes. IX. Sex Chromosomes of the Greater Glider (Marsupialia : Petauridae)

1979 ◽  
Vol 32 (3) ◽  
pp. 375 ◽  
Author(s):  
JD Murray ◽  
GM McKay ◽  
GB Sharman
Keyword(s):  
X Chromosome ◽  
Sex Chromosomes ◽  
National Park ◽  
Secondary Constriction ◽  
X Chromosomes ◽  
Cultured Fibroblasts ◽  
Multiple Sex Chromosomes ◽  
Eastern Australia ◽  
Xy Bivalent ◽  
Secondary Constrictions

The greater glider, currently but incorrectly known as Schoinobates vo/ans, is widely distributed in forested regions in eastern Australia. All animals studied from six different localities had 20 autosomes but there were four chromosomally distinct populations. At Royal National Park, N.S.W., all female greater gliders studied had 22 chromosomes including two large submetacentric X chromosomes with subterminal secondary constrictions in their longer arms. This form of X chromosome occurred also at Bondo State Forest, Myall Lakes and Coff's Harbour, N.S.W., and at Eidsvold, Qld. At Coomooboolaroo, Qld, the X chromosome was also a large submetacentric but a secondary constriction occurred in the shorter arm. Two chromosomally distinct types apparently occur in Royal National Park, one with XY m,ales as in all other populations, and one with XY1Y2 males. Y or Yb but not Y 2, chromosomes were eliminated from the bone marrow in all populations but were present in spermatogonia, primary sperrnatocytes and cultured fibroblasts. Animals from Bondo State Forest had three or more acrocentric or metacentric supernumerary chromosomes. [Other keywords: C-banding, eytotaxonomy, multiple sex chromosomes, XY bivalent.]

Cytogenetic studies in gomphocerine grasshoppers. II. Chromosomal location of active nucleolar organizing regions

1986 ◽  
Vol 28 (4) ◽  
pp. 540-544 ◽  
Author(s):  
Josefa Cabrero ◽  
Juan Pedro M. Camacho
Keyword(s):  
Chromosomal Location ◽  
Nucleolar Organizer ◽  
X Chromosomes ◽  
Nucleolar Organizing Regions ◽  
Nucleolar Organizing Region ◽  
Primary Activity ◽  
Cytogenetic Studies ◽  
Almost All ◽  
Active Nors

Nucleolar organizing region (NOR) location has been studied in 20 species of gomphocerine grasshoppers. In the 17 species with 2n (♀) = 17, the largest number carry an active NOR on the L2, L3, and X chromosomes. The M4, M5, M6, and S8 show NOR activity in some species, but the L1 and M7 do not carry a NOR in any. While almost all NORs on L2, L3, and X show primary activity, a majority of these on the M4, M5, M6, and S8 are secondary and express a nucleolus only in a minority of male meiocytes. The NORs are located preferentially at particular chromosomal sites; primary active NORs prevail in interstitial locations, while secondary active NORs predominate in paracentromeric locations. In the majority of the species analyzed in this report, primary and secondary active NORs coincide with C-bands. Euchorthippus pulvinatus is an exception; here NORs do not seem to be related to C-bands. However, the nucleolar-associated heterochromatin in this species can be demonstrated by a N-banding technique.Key words: nucleolar organizer, NOR (primary), C-bands, heterochromatin, NOR (secondary).

Genetic analysis of sterility in hybrids from crosses of Glossina morsitans submorsitans and Glossina morsitans centralis (Diptera: Glossinidae)

1993 ◽  
Vol 71 (10) ◽  
pp. 1963-1972 ◽  
Author(s):  
R. H. Gooding
Keyword(s):  
Y Chromosome ◽  
Lower Probability ◽  
Glossina Morsitans ◽  
Hybrid Male ◽  
X Chromosomes ◽  
Glossina Morsitans Submorsitans ◽  
Glossina Morsitans Centralis ◽  
Recurrent Backcrossing ◽  
Almost All ◽  
Glucose 6 Phosphate Dehydrogenase

When genetically marked Glossina morsitans submorsitans Newstead were mated to Glossina morsitans centralis Machado, viable offspring were obtained when using G. m. submorsitans females but not when using G. m. centralis females. The maternally inherited sterility factor, from G. m. submorsitans, that causes this asymmetry was inactivated or replaced during recurrent backcrossing to G. m. centralis. F1 hybrid males were sterile but most F1 hybrid females were fertile. There was little evidence for differential transmission of G. m. submorsitans and G. m. centralis chromosomes by hybrid females. Almost all backcross males were sterile if they had an X and a Y chromosome from two different taxa; the exceptional males had recombinant X chromosomes. The X chromosome locus for X/Y compatibility lies closer to the locus for esterase-X than to the locus for glucose-6-phosphate dehydrogenase. Heterozygosity in linkage group II is also a factor in causing hybrid male sterility; the locus for compatibility is closer to the locus for octanol dehydrogenase than to the locus for esterase-1. Among the backcross males that had an X and a Y chromosome from the same taxon, 12% of those obtained by backcrossing to G. m. centralis were fertile and 65% of those obtained by backcrossing to G. m. submorsitans were fertile. Backcrossing F1 hybrid females to G. m. submorsitans produced females that were equally likely to be fertilized by G. m. submorsitans and G. m. centralis. However, backcrossing to G. m. centralis produced females that had a much lower probability of being fertilized by G. m. submorsitans than by G. m. centralis.

Sign in / Sign up

Export Citation Format

Share Document