Answer to Question #155205 in Genetics for Ashwani Kumar Gupta

Question

Hypertrichosis is inherited as a trait linked to the Y-chromosome, which manifests itself by 17 years of age. One of the forms of ichthyosis (scaly, patchy thickening of the skin) is inherited as a recessive trait linked to the X chromosome. In a family where the woman is normal, and the husband has only hypertrichosis, a boy was born with signs of ichthyosis.

a) Determine the likelihood of this boy showing hypertrichosis?

b) Determine the probability of birth in this family of children without anomalies and what gender will they be?

Answer 1

a) The boy won't be affected since an affected male will pass this form of hypertrichosis to his daughters, but will never pass it to the sons.

b) The probability is 50% or $\frac{1} {2}$ and the gender will be male since the male parent doesn't transmit the trait to sons.