CBSE 2022 · Region 1 · Set 3 · Q15

The mechanism by which the sex of an individual is determined is called sex-determination. In human beings, sex of a newborn is genetically determined, whereas in some others it is not. There are $\displaystyle 46$ ($\displaystyle 23$ pairs) chromosomes in human beings. Out of these, $\displaystyle 44$ ($\displaystyle 22$ pairs) control the body characters and $\displaystyle 2$ (one pair) are known as sex chromosomes. The sex chromosomes are of two types - X chromosome and Y chromosome. At the time of fertilisation, depending upon which type of male gamete fuses with the female gamete, the sex of the newborn child is decided.

(a)

What is the statistical probability of getting either a male or a female child ? Justify your answer. $\displaystyle \frac{1}{2}+\frac{1}{2}$

(b)

Out of male or female, which of them has a perfect pair of sex chromosomes ? In case of a perfect pair, will the gametes produced be of the same kind or of a different kind ?

(c)

(i)OR(ii)

Name two animals whose sex is not genetically determined. Explain the process of their sex determination.