Question

A certain couple got only four daughters in a row and no son. Does it mean that the husband does not produce Y-bearing sperms? Explain.

Answer 1

No, it does not mean that the husband does not produce Y-bearing sperms.
Sex of the child depends upon the kind of sperm that fertilizes the egg. The egg contains only one X chromosome, but half of the sperms released into the female are X-bearing and the remaining half are Y-bearing. It is simply a matter of chance as to which category of sperms fuses with the ovum. If the egg (X) is fused by X-bearing sperm, the resulting combination is XX, i.e. female type, and the child produced is female (daughter). If the egg (X) is fused by Y-bearing sperm, the resulting combination is XY, i.e. male constitution, and the child produced will be a male (son).