Question

List whether each of these chromosome combinations will lead to the development of males or females in mammals.
XY XYY XO XXY

Answer 1

SRY gene located at Y chromosome determines sex differentiation and male gonad development. Presence of Y chromosome in zygote of mammals will lead to the development of male animal in most cases. Male sex determination by Y chromosome is not dependent on number of X chromosome copies present in zygote cell. In exceptional cases a female animal will develop with Y chromosome in zygote cell, chance of which is very low.

XY - In this case a normal fertile male will develop.

XYY - In this case a male animal with normal sex organs will develop. But the chances of being fertile is very low, because distribution of X and Y chromosome into sperms will not be balanced. This condition is called Jacob's syndrome.

XO - In this case a female animal will develop because of lack of Y chromosome in zygote. Developed female will be sterile and will have some physical abnormalities. This condition is called Turner syndrome.

XXY - In this case a sterile male with underdeveloped sex organs will develop. This type of males may possess few female morphological characteristics. This condition is called Klinefelter's syndrome.