Biology probability

In some families, hair colour is inherited with a dominant/recessive pattern of inheritance. Brown hair is encoded by the dominant allele and blonde hair by the recessive allele. Two babies are born into families with this pattern of inheritance. Adam’s parents are both heterozygous. Anne has one parent who is homozygous recessive and one who is heterozygous.

What is the probability that both Adam and Anne have the same hair colour?

A. 3/64
B. 1/8
C. 3/8
D. 1/2
E. 1


for Adam: 3/4 brown, 1/4 blonde

for Anne: 1/2 brown, 1/2 blonde

so if both want to have same colour:

brown: 3/4 * 1/2 = 3/8

blonde: 1/4 * 1/2 = 1/8

to have the same its blonde or brown: 3/8 + 1/8 = 4/8 = 1/2


Thanks @DariusDuhan
I got your calculation. To find the probability of mutual event we need product rule of probability and to find probability of two exclusive events we need to do addition rule.

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Exactly, good job Ibraheem!

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