[Bird sex determination].
During the evolution, sex determination occurred early. Sex determining factors were progressively isolated from other genes in sexual chromosomes, or gonosomes. Among vertebrates, evolution took two opposite pathways : in mammals, the system of XX:XY sex determination, with Y chromosome, induces male differentiation. In contrast, in birds, the system ZZ:ZW, with the W chromosome, induces female differentiation. But comparative studies show that the two pathways are not so simple. In the chicken as in the lower vertebrates, estrogens play a central role in gonadal sex differentiation. Several genes, show to be critical for mammalian determination, are also expressed in the chicken but their expression pattern differs, indicating functional plasticity. The W-linked female determinants remains still unknown. But comparative studies of the two pathways, with conserved and divergent elements, are broadening our understanding of sex determination.
Gilgenkrantz
Simone
S
simone.gilgenkrantz@ club-internet.fr
D000818:Animals; D005075:Biological Evolution; D001717:Birds / Q000235:genetics* / Q000502:physiology*; D002645:Chickens / Q000235:genetics / Q000502:physiology; D004967:Estrogens / Q000494:pharmacology; D005260:Female; D008297:Male; D012730:Sex Chromosomes; D019849:Sex Determination Processes
D004967:Estrogens