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Sex determination in mammals — Before and after the evolution of SRY
. Therian mammals (marsupials and placentals) have an XX female: XY male sex chromosome system, which is homologous to autosomes in other vertebrates. The testis-determining gene, SRY , is conserved on the Y throughout therians, but is absent in other vertebrates, suggesting that the mammal system e...
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Published in: | Cellular and molecular life sciences : CMLS 2008-10, Vol.65 (20), p.3182-3195 |
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Main Authors: | , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that cite this one |
Online Access: | Get full text |
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Summary: | .
Therian mammals (marsupials and placentals) have an XX female: XY male sex chromosome system, which is homologous to autosomes in other vertebrates. The testis-determining gene,
SRY
, is conserved on the Y throughout therians, but is absent in other vertebrates, suggesting that the mammal system evolved about 310 million years ago (MYA). However, recent work on the basal monotreme mammals has completely changed our conception of how and when this change occurred. Platypus and echidna lack
SRY
, and the therian X and Y are represented by autosomes, implying that
SRY
evolved in therians after their divergence from monotremes only 166 MYA. Clues to the ancestral mechanism usurped by
SRY
in therians are provided by the monotremes, whose sex chromosomes are homologous to the ZW of birds. This suggests that the therian X and Y, and the
SRY
gene, evolved from an ancient bird-like sex chromosome system which predates the divergence of mammals and reptiles 310 MYA. |
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ISSN: | 1420-682X 1420-9071 |
DOI: | 10.1007/s00018-008-8109-z |