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Sep. 10th, 2015 06:19 pmIn humans and other placental mammals, the presence or absence of a Y chromosome determines sex.
The SRY gene is responsible for the development of testosterone, testes, etc.
In Drosophila, sex is determined by the ratio of X chromosomes to autosomes.
In birds, butterflies, and some reptiles, males produce ZZ instead of XY, and females produce XW.
In honeybees, sex is determined by whether the animal is haploid or diploid.
If you have 2 X chromosomes in females and 1 in male, either:
1. The X gene works twice as hard in males (Drosophila)
2. One X gene is deactivated in females (mammals)
3. Each X gene works half as hard in females (nematode)
In mammals, either the maternal or paternal chromosome is deactivated at random in each cell. Females are mosaics.
The SRY gene is responsible for the development of testosterone, testes, etc.
In Drosophila, sex is determined by the ratio of X chromosomes to autosomes.
In birds, butterflies, and some reptiles, males produce ZZ instead of XY, and females produce XW.
In honeybees, sex is determined by whether the animal is haploid or diploid.
If you have 2 X chromosomes in females and 1 in male, either:
1. The X gene works twice as hard in males (Drosophila)
2. One X gene is deactivated in females (mammals)
3. Each X gene works half as hard in females (nematode)
In mammals, either the maternal or paternal chromosome is deactivated at random in each cell. Females are mosaics.
