Question

pedigree
what is the predicted genotype of i1 and i2 (the father and mother at the top of the chart).
a xy and xx
b $x^hy$ and $x^hx$
c $x^hy$ and $x^hx^h$
d $x^hy^h$ and $x^hx^h$

Explanation:

This is an X-linked recessive trait (affected males inherit the mutant allele from carrier mothers, unaffected females can pass it to sons). The top father (I1) is unaffected, so he has the dominant allele on his X chromosome: $X^H Y$. The top mother (I2) is unaffected but has affected sons, meaning she is a carrier with one dominant and one recessive allele: $X^H X^h$. This matches option C.

Answer:

C. $X^H Y$ and $X^H X^h$