Question

A woman carrier for haemophilia marries a normal man. Predict the possible genotypes and phenotypes of the offspring using a Punnett square. Also state percentages.

Hint:

Haemophilia is a sex-linked recessive disorder, which is why it predominantly affects males.

Answer 1

Step 1: Parental Genotypes - Carrier Mother: $X^{H}X^{h}$; Normal Father: $X^{H}Y$.
Step 2: Punnett Square - The cross yields four genotypes: $X^{H}X^{H}$ (Normal Female), $X^{H}X^{h}$ (Carrier Female), $X^{H}Y$ (Normal Male), and $X^{h}Y$ (Haemophilic Male).
Step 3: Statistics - (a) Normal males: 25% of total offspring (or 50% of all sons). (b) Carrier for haemophilia: 25% of total offspring (or 50% of all daughters).