Question

In humans, the ABO blood type is under control of autosomal multiple alleles. Red-green colorblindness is a recessive X-linked trait. If two parents who are both type A and have normal vision produce a son who is colorblind and type O, what is the probability that their next child will be a female who has normal vision and is type O?

Answer 1

1/8

Step-by-step explanation:

Father: normal vision, type A

Mother: normal vision, type A

They can only produce a colourblind son if female is the carrier for it:

XC Xc

XC XCXC XCXc

Y XCY XcY

XcY son will be colorblind. Hence father has XCY genotype and mother has XCXc genotype for vision.

They can only produce type O son if both of them are heterozygous for type A:

A O

A AA AO

O AO OO

OO son will have type O blood. Hence both father and mother have AO genotype for blood type.

Probability of having a female child=1/2

Probability of having a normal vision female child = 1 since in the first punnett square it has been shown that all female children have normal vision ( half are carriers )

Probability of having type O child = 1/4

Probability of having a female child with normal vision and type O blood = 1/2 * 1 * 1/4 = 1/8