Question

The sex chromosomes in male are indicated by
a) XY
b) XX
c) YY
d) XXYY

Answer 1

As we know humans have twenty three pairs of chromosomes. Out of these, twenty two pairs are called as autosomes which are opposite of sex chromosomes and they control the inheritance of an organism's characteristics except the sex-linked one and only one pair is the sex chromosome, which actively takes part in the process of sex determination. Both males and females carries only two sets of sex chromosome.

Complete answer:
The XY sex-determination system is found in humans, mammals, some insects and in few plant species. In this system, the sex of an individual is determined by a pair of sex chromosomes also called as gonosomes.
All children will inherit an X chromosome from their mother, despite being a boy or a girl. Thus, the sex of the children will be determined by the type of chromosome which is inherited from their father. Therefore, a child who inherits Y chromosome will be a boy and a girl who inherits X chromosome will be a girl.
Therefore we can say that option B is incorrect because XX are the sex chromosomes in female.
Option C is also incorrect because YY cannot be used for sex determination as the child will always receive X chromosome from the mother.
Whereas in option D, which says XXYY is also incorrect because the child inherits X chromosome from the mother and X or Y chromosome from the father. Hence there should only be two alleles.

Hence we can say that sex chromosomes in male are indicated by XY therefore option A is correct.

Note:
Females have two of the same kind of sex chromosome denoted as XX and hence are called as the homogametic sex. Males have two distinct sex chromosomes, XY and are called as the heterogametic sex. A male semen holds approximately fifty percent of Y sperm cells and other fifty percent of X sperm cells. Therefore, there are possibilities that men have three or more children of a single-gender.