Half-cocked

[Horwood Beer-Master]

Gender-Bending Chickens: Mixed, Not Scrambled

...It was widely assumed that sexual development in birds and mammals follows basically the same trajectory. In almost all mammals, including humans, embryonic cells start off being "unisex"; indistinguishable regardless of which sex chromosomes they contain. Early in development, the sex-determining region of the Y chromosome (Sry) controls whether a testis or ovary forms: if Sry is present, testes grow, while ovaries develop in the absence of Sry. By the seventh week of embryonic life, the developing gonads begin secreting chemical messengers -- hormones -- that direct other cells to develop as either male or female.

Given this paradigm, scientists studying gynandromorphs were surprised to discover that sexual development in birds is dramatically different from most mammals: unlike mammals, individual chicken cells apparently "know" which sex they are at the time of fertilization and they maintain their own male or female identities throughout life...

[Bella Fortuna]

How fascinating!