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. [3 MARKS]

Formation of new progeny:

1. Sex of the child depends upon the kind of sperm that fertilizes the egg.
   
2. 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.
   
3. It is simply a matter of chance as to which category of sperms fuses with the ovum.
   
4. 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).
   
5. 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).
6. So, it does not mean that the husband does not produce Y-bearing sperms.