Sex chromosomes: platypus genome suggests a recent origin for the human X.
The unusual sex chromosomes of platypus are not homologous to the human X and Y chromosomes, implying that the sex chromosomes of placental mammals evolved after the monotreme and placental mammal lineages split about 165 million years ago.
Ellegren
Hans
H
Department of Evolutionary Biology, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, SE-752 36 Uppsala, Sweden. Hans.Ellegren@ebc.uu.se
D000818:Animals; D005075:Biological Evolution; D041321:Chromosomes, Human, X; D005260:Female; D006801:Humans; D008297:Male; D010987:Platypus / Q000235:genetics*; D012730:Sex Chromosomes; D019849:Sex Determination Processes