explain that it is a matter of chance whether a couple will give birth toto a boy or a girl

• Humans have 22 pairs of autosomes and 1 pair of sex chromosome.
• Male parent produces X bearing and Y bearing gametes or sperms.
• Female parent produces only X bearing gametes or eggs.
• During reproduction, the combination of X bearing gamete from males with one X bearing gamete from females results in offspring with genetic constitution– XX. The child produced is a female or a daughter.
• The combination of Y chromosome from males with one X chromosome from females results in an offspring with genetic constitution – XY. The child produced is a male or a son.
• Thus, the birth of a boy or a girl is purely a matter of chance and entirely depends on the type of sperm which fertilises the egg.