Following is a pedigree for albinism (aa). What is the probability of II -1 to be a heterozygous?

Question

Following is a pedigree for albinism (aa). What is the probability of II -1 to be a heterozygous? (A) (1/3) (B) (1/2) (C) (2/3) (D) (1/4)

Tardigrade Admin · Accepted Answer

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.

Q. Following is a pedigree for albinism (aa). What is the probability of II -1 to be a heterozygous?

$\frac{1}{3}$

$\frac{1}{2}$

$\frac{2}{3}$

$\frac{1}{4}$

Parents are heterozygous normal otherwise $II - 2$ could not be albino. Now cross between $2$ -heterozygous (Aa) produces $AA (1) : A a (2) : aa (1)$ . Since $II - 1$ is normal, the chances of a heterozygous (normal) child will be 2 out of three, i.e., 2/3.