Thank you for reporting, we will resolve it shortly
Q.
Following is a pedigree for albinism (aa). What is the
probability of II -1 to be a heterozygous?
Principles of Inheritance and Variation
Solution:
Parents are heterozygous normal otherwise $II-2$ could
not be albino. Now cross between $2$-heterozygous (Aa)
produces $AA (1) : Aa (2) : aa (1)$. Since $II-1$ is normal, the
chances of a heterozygous (normal) child will be 2 out of
three, i.e., 2/3.
