Question

We know that on;y one chromosome from father is transfer to other chromosome of mother. If Y chromosome a dad connected to X chromosome frm female . and only a pair involves then how will the twins(one boy one girl) formed??

Answer 1

Dear student,

As the male and female gametes are haploid in nature, the female gamete (egg) would have only X chromosome but the male gamete(sperm) either have X or Y chromosome.
When one sperm with X chromosome and one with Y chromosome fertilizes two different eggs(with X chromosome) of the same female, there is the development of two fetus together. These two fetus are unrelated to each other; one may be male or other may be female developing inside the same uterus. Such twins are called fraternal twins.

Regards.