The Hopi, Zuni, and other Southwest American Indians have a relatively high frequency of albinism resulting from homozygosity for a recessive allele, a. A normally pigmented man and woman, each of whom has an albino parent, have two children. a) What is the probability that both children are albino? b) What is the probability that at least one of the children is albino? Solution Answer: a. Each parent had an albino parent, therefore, they have the recessive allele though are still normal because they have a dominant allele as well. Aa (Dad) x Aa (Mom) = 1/4 (AA), 1/2 (Aa), 1/4 (aa) Each birth has a 1/4 chance of being albino, therefore, in order for them both to be albino = 1/4 *1/4 = 1/16 b. To get at least one albino child, we can have a combination of: Normal Child (First Birth), Albino Child (Second Birth) = 3/4*1/4 = 3/16 Albino Child (First Birth), Normal Child (Second Birth) = 1/4*3/4 = 3/16 Albino Child (First Birth), Albino Child (Second Birth) = 1/4*1/4 = 1/16 3/16 + 3/16 + 1/16 = 7/16.

1. The Hopi, Zuni, and other Southwest American Indians have a relatively high frequency of
albinism resulting from homozygosity for a recessive allele, a. A normally pigmented man and
woman, each of whom has an albino parent, have two children.
a) What is the probability that both children are albino?
b) What is the probability that at least one of the children is albino?
Solution
Answer:
a. Each parent had an albino parent, therefore, they have the recessive allele though are still
normal because they have a dominant allele as well.
Aa (Dad) x Aa (Mom) = 1/4 (AA), 1/2 (Aa), 1/4 (aa)
Each birth has a 1/4 chance of being albino, therefore, in order for them both to be albino = 1/4
*1/4 = 1/16
b. To get at least one albino child, we can have a combination of:
Normal Child (First Birth), Albino Child (Second Birth) = 3/4*1/4 = 3/16
Albino Child (First Birth), Normal Child (Second Birth) = 1/4*3/4 = 3/16
Albino Child (First Birth), Albino Child (Second Birth) = 1/4*1/4 = 1/16
3/16 + 3/16 + 1/16 = 7/16