There are 23 pairs of chromosomes present in human beings.
There is 1 pair of sex chromosomes present in human beings.
The chromosomes which determines the sex of a person are called sex chromosomes. There are two types of sex chromosomes, one is called X chromosomes and the other is called Y chromosome. Male contain one X chromosome and one Y chromosome ( XY) , while females contain two X chromosomes (X X).
Flor chart showing determination of sex of a child.
(i) A male has one X-chromosome and one Y-chromosome. Thus, half the male gametes have X-chromosomes and the other half have Y-chromosomes.
(ii) A female has two X-chromosomes. Thus all female gametes have only X-chromosomes.
(iii) If a sperm carrying Y-chromosome fertilises an ovum carrying X-chromosome, then the child born will be a boy.
(iv) If a sperm carrying X-chromosome fertilises an ovum carrying X-chromosome, then the child born will be a girl.
Therefore it is the sperm from the father which determines the sex of the child.