Explain sex determination mechanism in humans.How is it different in birds?
CBSE Class 12
CBSE Class 12 Biology
2016-08-29 12:59:44 UTC
Sex determining mechanism in humans is XY type. Out of 23 pairs of chromosomes present, 22 are autosomes.A Pair of X chromosomes is present in females, whereas an X and Y chromosome are present in males.During spermatogenesis among males,two types of gametes are produced.
2.50 percent of the total sperm produced carry the X chromosome and the rest 50 percent has Y chromosome.In case, the ovum fertilizes with the sperm carrying X chromosomes the Zygote develops into female ('XX') and with 'Y' chromosomes the zygote results into male offspring(XY).
In birds, female birds have been designated to have Z and W chromosomes, whereas males have a pair of Z chromosomes besides autosomes.