Q. 4. How is the sex of the child determined in human beings?
Half the male gametes have X-chromosomes and the other half have Y-chromosomes human male has one X-chromosome and one Y-chromosome. In other words, The human male has one X chromosome and one Y chromosome On the other hand, all female gametes have only X chromosomes. If a sperm carrying a Y-chromosome fertilizes an ovum then the child born will be a boy.
On the other hand, if a sperm carrying X-chromosomes fertilizes an ovum then the child born will be a girl.
X + X = Girl
X + Y = Boy.