Distribution of Constitutive Heterochromatin and the Evolution of Sex Chromosomes in Fundulus

Copeia ◽  
1981 ◽  
Vol 1981 (4) ◽  
pp. 916 ◽  
Author(s):  
Irv Kornfield
Keyword(s):  
Sex Chromosomes ◽  
Constitutive Heterochromatin ◽  
Evolution Of Sex

CHROMOSOMES AND DNA OF MICROTUS II. CONFIRMATION OF DELETION OF CONSTITUTIVE HETEROCHROMATIN IN M. AGRESTIS CELLS IN VITRO

1977 ◽  
Vol 19 (3) ◽  
pp. 537-541 ◽  
Author(s):  
J. E. K. Cooper
Keyword(s):  
Somatic Cell ◽  
Cell Line ◽  
Cell Lines ◽  
X Chromosome ◽  
Sex Chromosomes ◽  
Constitutive Heterochromatin ◽  
The Other ◽  
Microtus Agrestis ◽  
C Banding

The distribution of constitutive heterochromatin has been examined by C-banding in two somatic cell lines, grown in vitro, from a female Microtus agrestis. One line retains one intact X chromosome together with the short arm of the other X chromosome, while the other cell line retains only the short arm of one X chromosome. Thus, each cell line has lost substantial amounts of heterochromatin from the sex chromosomes, but this material has been deleted from the cells, and not translocated to other chromosomes. Nonetheless, both cell lines continue to propagate well in vitro.

scholarly journals Distribution of constitutive heterochromatin in species of triatomines with fragmentation of sex chromosomes X

2014 ◽  
Vol 13 (4) ◽  
pp. 10279-10284 ◽  
Author(s):  
A.L. Guerra ◽  
K.C.C. Alevi ◽  
J.A. Rosa ◽  
M.T.V. Azeredo-Oliveira
Keyword(s):  
Sex Chromosomes ◽  
Constitutive Heterochromatin

scholarly journals Meiotic Behavior of Achiasmate Sex Chromosomes in the African Pygmy Mouse Mus mattheyi Offers New Insights into the Evolution of Sex Chromosome Pairing and Segregation in Mammals

Genes ◽  
2021 ◽  
Vol 12 (9) ◽  
pp. 1434
Author(s):  
Ana Gil-Fernández ◽  
Marta Ribagorda ◽  
Marta Martín-Ruiz ◽  
Pablo López-Jiménez ◽  
Tamara Laguna ◽  
...  
Keyword(s):  
Dna Repair ◽  
Y Chromosome ◽  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Mammalian Species ◽  
Evolutionary Process ◽  
Small Region ◽  
Pseudoautosomal Region ◽  
Evolution Of Sex ◽  
African Pygmy Mouse

X and Y chromosomes in mammals are different in size and gene content due to an evolutionary process of differentiation and degeneration of the Y chromosome. Nevertheless, these chromosomes usually share a small region of homology, the pseudoautosomal region (PAR), which allows them to perform a partial synapsis and undergo reciprocal recombination during meiosis, which ensures their segregation. However, in some mammalian species the PAR has been lost, which challenges the pairing and segregation of sex chromosomes in meiosis. The African pygmy mouse Mus mattheyi shows completely differentiated sex chromosomes, representing an uncommon evolutionary situation among mouse species. We have performed a detailed analysis of the location of proteins involved in synaptonemal complex assembly (SYCP3), recombination (RPA, RAD51 and MLH1) and sex chromosome inactivation (γH2AX) in this species. We found that neither synapsis nor chiasmata are found between sex chromosomes and their pairing is notably delayed compared to autosomes. Interestingly, the Y chromosome only incorporates RPA and RAD51 in a reduced fraction of spermatocytes, indicating a particular DNA repair dynamic on this chromosome. The analysis of segregation revealed that sex chromosomes are associated until metaphase-I just by a chromatin contact. Unexpectedly, both sex chromosomes remain labelled with γH2AX during first meiotic division. This chromatin contact is probably enough to maintain sex chromosome association up to anaphase-I and, therefore, could be relevant to ensure their reductional segregation. The results presented suggest that the regulation of both DNA repair and epigenetic modifications in the sex chromosomes can have a great impact on the divergence of sex chromosomes and their proper transmission, widening our understanding on the relationship between meiosis and the evolution of sex chromosomes in mammals.

KARYOLOGICAL STUDIES OF A FEMALE VARIABLE OYSTERCATCHER (HAEMATOPUS UNICOLOR)

1981 ◽  
Vol 23 (4) ◽  
pp. 611-619 ◽  
Author(s):  
Allan J. Baker ◽  
M. Parslow ◽  
D. Chambers
Keyword(s):  
Sex Chromosomes ◽  
Constitutive Heterochromatin ◽  
Medium Size ◽  
W Chromosome ◽  
Valuable Data ◽  
Diploid Complement ◽  
Embryo Cells

The chromosomes of Haematopus unicolor Forster were examined from cultures of embryo cells. The diploid complement for one individual was estimated to be 2n = 72, comprising 35 autosomes and a pair of sex chromosomes. The W chromosome is a medium size submetacentric. It is smaller than the Z and is the only chromosome with noncentromeric constitutive heterochromatin. The only other species of this genus whose karyotype is known, H. ostralegus, differs from H. unicolor in having a smaller diploid complement (2n = 66) and a telocentric W chromosome. Comparative karyological studies of other species will likely provide valuable data for clarifying the systematics of the Haematopodidae.

scholarly journals Independent Evolution of Sex Chromosomes in Eublepharid Geckos, a Lineage with Environmental and Genotypic Sex Determination

2020 ◽  
Author(s):  
Eleonora Pensabene ◽  
Lukáš Kratochvíl ◽  
Michail Rovatsos
Keyword(s):  
Sex Determination ◽  
Sex Chromosomes ◽  
Gene Content ◽  
Gene Copy ◽  
Specific Gene ◽  
Evolution Of Sex ◽  
Copy Numbers ◽  
Genotypic Sex Determination ◽  
The Difference ◽  
Genomic Regions

Geckos demonstrate a remarkable variability in sex determination systems, but our limited knowledge prohibits accurate conclusions on the evolution of sex determination in this group. Eyelid geckos (Eublepharidae) are of particular interest, as they encompass species with both environmental and genotypic sex determination. We identified for the first time the X-specific gene content in the Yucatán banded gecko, Coleonyx elegans, possessing X1X1X2X2/X1X2Y multiple sex chromosomes by comparative genome coverage analysis between sexes. The X-specific gene content of Coleonyx elegans was revealed to be partially homologous to genomic regions linked to the chicken autosomes 1, 6 and 11. A qPCR-based test was applied to validate a subset of X-specific genes by comparing the difference in gene copy numbers between sexes, and to explore the homology of sex chromosomes across 11 eublepharid, two phyllodactylid and one sphaerodactylid species. Homologous sex chromosomes are shared between Coleonyx elegans and Coleonyx mitratus, two species diverged approximately 34 million years ago, but not with other tested species. As far as we know, the X-specific gene content of Coleonyx elegans / Coleonyx mitratus was never involved in the sex chromosomes of other gecko lineages, indicating that the sex chromosomes in this clade of eublepharid geckos evolved independently.

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