Journal ArticleDOI
Chromosome banding in Amphibia. VIII. An unusual XY/XX-sex chromosome system in Gastrotheca riobambae (Anura, Hylidae).
TLDR
The mitotic and meiotic chromosomes of the marsupial frog Gastrotheca riobambae were analysed with various banding techniques and it is shown that the constitutive heterochromatin in the Y chromosome consists of at least three different structural categories.Abstract:
The mitotic and meiotic chromosomes of the marsupial frog Gastrotheca riobambae were analysed with various banding techniques. The karyotype of this species is distinguished by considerable amounts of constitutive heterochromatin and unusual, heteromorphic XY sex chromosomes. The Y chromosome is considerably larger than the X chromosome and almost completely heterochromatic. The analysis of the banding patterns obtained with GC- and AT-base-pair-specific fluorochromes shows that the constitutive heterochromatin in the Y chromosome consists of at least three different structural categories. The only nucleolus organizer region (NOR) of the karyotype is localized in the short arm of the X chromosome. This causes a sex-specific difference in the number of NOR: female animals have two NORs in diploid cells, male animals one. No cytological indications were found for the inactivation of one of the two X chromosomes in the female cells. In male meiosis, the heteromorphic sex chromosomes form a characteristic sex-bivalent by pairing their telomeres in an end-to-end arrangement. The significance of the XY/XX sex chromosomes of G. riobambae for the study of X-linked genes in Amphibia, the evolution of sex chromosomes and their specific DNA sequences, and the significance of the meiotic process of sex chromosomes are discussed.read more
Citations
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Journal ArticleDOI
Chromosome banding in Amphibia. XXVIII. Homomorphic XY sex chromosomes and a derived Y-autosome translocation in Eleutherodactylus riveroi (Anura, Leptodactylidae).
TL;DR: Extensive cytogenetic analyses on a population of the leptodactylid frog Eleutherodactylus riveroi in northern Venezuela revealed the existence of multiple XXAA♂/XYAA♀/XAAY as discussed by the authors.
Journal ArticleDOI
An XX/XY sex chromosome system in a fish species, Hoplias malabaricus, with a polymorphic NOR-bearing X chromosome.
TL;DR: The present results confirm the XX/XY sex chromosome system in the population analyzed as well as a new cytotype in the Hoplias malabaricus group, confirming a polymorphic size condition observed in the X chromosome.
Journal ArticleDOI
Different origins of bird and reptile sex chromosomes inferred from comparative mapping of chicken Z-linked genes.
TL;DR: The absence of homology between the bird Z chromosome and the snake and turtle Z sex chromosomes suggests that the origin of the sex chromosomes and the causative genes of sex determination are different between birds and reptiles.
Journal ArticleDOI
Quantitative determination of rDNA transcription units in vertebrate cells
TL;DR: The adenosine analogue 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB) unravels the compact nucleoli to necklace-like structures when applied to living cells, implying that formerly inactive rRNA genes are recruited for transcription.
Journal ArticleDOI
High tandem repeat content in the genome of the short-lived annual fish Nothobranchius furzeri: a new vertebrate model for aging research.
Kathrin Reichwald,Chris Lauber,Chris Lauber,Indrajit Nanda,Jeanette Kirschner,Nils Hartmann,Susanne Schories,Ulrike Gausmann,Stefan Taudien,Markus Schilhabel,Markus Schilhabel,Karol Szafranski,Gernot Glöckner,Michael Schmid,Alessandro Cellerino,Manfred Schartl,Christoph Englert,Matthias Platzer +17 more
TL;DR: This work presents a first basis for systematic genomic and genetic analyses aimed at understanding the mechanisms of life span determination in N. furzeri and provides a first insight into its genome and a comparison to medaka, stickleback, tetraodon and zebrafish.
References
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Journal ArticleDOI
New Giemsa method for the differential staining of sister chromatids
Paul Perry,Sheldon Wolff +1 more
TL;DR: If human lymphocytes1 or Chinese hamster2 cells are treated with the base analogue 5-bromodeoxyuridine in the latter part of the S period, Giemsa stained chromosomes exhibit a pattern of condensed and extended segments along their length, allowing the identification of the two chromatids, and the observation of sister chromatid exchanges (SCEs) without recourse to autoradiography.
Book
Evolution of sex determining mechanisms
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