Zoology - Principles of Inheritance and Variation Question with Solution | TestHub

Haemophilia is a sex linked disease. It follows criss-cross inheritance in which father does not pass the sex-linked allele of a trait to his son. The same is passed to the daughter, from where it reaches the grandson, i.e., diagynic. It is because the males have only one $\mathrm{X}$-chromosome which is transferred to the female offspring. Only Y-chromosome of the father is transferred to the male offspring but this sex chromosome does not carry the allele for haemophilia. Mother passes the alleles of a sex-linked trait to both sons and daughters.