Solutions For An Introduction to Genetic Analysis Chapter 2 Problem 46P

When both the husband and wife are heterozygous, for a recessive allele, for albinism, the resultant will be dizygotic twins. The probability of both the twins will have the same phenotype, for pigmentation.

For instance, if both are A/a, then the cross is A/a X A/a.

Probability of being normal (A/a) is 3/4

Probability of being an albino (a/a) is 1/4

The dizygotic twins will phenotypically are same and both of them should be normal or both of them should be albino.

Therefore, the probability of having same phenotype = probability of both normal + Probability of both albino.

Probability of both normal = Probability of first normal X probability of second normal

= 3/4 X3/4 = 9/16

Probability of both albino = Probability of first albino X Probability of second albino

= 1/4 X1/4 = 1/16

Hence, the probability of both has same phenotype: