Dynamics of vertebrate sex chromosome evolution: from equal size to giants and dwarfs

The Y and W chromosomes of mammals and birds are known to be small because most of their genetic content degenerated and were lost due to absence of recombination with the X or Z, respectively. Thus, a picture has emerged of ever-shrinking Ys and Ws that may finally even fade into disappearance. We...

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Bibliographic Details
Published in:Chromosoma 2016-06, Vol.125 (3), p.553-571
Main Authors: Schartl, Manfred, Schmid, Michael, Nanda, Indrajit
Format: Article
Language:English
Subjects:
Amphibians
Animal Genetics and Genomics
Animals
Biochemistry
Biomedical and Life Sciences
Birds
Cell Biology
Developmental Biology
Eukaryotic Microbiology
Evolution, Molecular
Female
Fishes
Heterochromatin - genetics
Human Genetics
Life Sciences
Male
Mice
Reptiles
Review
Sex Determination Processes - genetics
X Chromosome - genetics
Y Chromosome - genetics
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Summary:The Y and W chromosomes of mammals and birds are known to be small because most of their genetic content degenerated and were lost due to absence of recombination with the X or Z, respectively. Thus, a picture has emerged of ever-shrinking Ys and Ws that may finally even fade into disappearance. We review here the large amount of literature on sex chromosomes in vertebrate species and find by taking a closer look, particularly at the sex chromosomes of fishes, amphibians and reptiles where several groups have evolutionary younger chromosomes than those of mammals and birds, that the perception of sex chromosomes being doomed to size reduction is incomplete. Here, sex-determining mechanisms show a high turnover and new sex chromosomes appear repeatedly. In many species, Ys and Ws are larger than their X and Z counterparts. This brings up intriguing perspectives regarding the evolutionary dynamics of sex chromosomes. It can be concluded that, due to accumulation of repetitive DNA and transposons, the Y and W chromosomes can increase in size during the initial phase of their differentiation.
ISSN:0009-5915
1432-0886
DOI:10.1007/s00412-015-0569-y