According to the question
B → Brown hair
b → bloude hair
The two mating partners are heterozygous
∴ Probability for a brown haired progeny (p) = 3/4
Probability for a blonde haired progeny (q) = 1/4
According to the question, at least one of the next three progenies have blonde hair. Therefore, following combinations of binomials will satisfy the condition-
(1) Only one progeny of the three has blonde hair
(2) Two of the three progenies have blonde hair
(3) All of them have blonde hair
Using binomial expression. the Probabilities of each possible combination can be calculated as
(1) n = 3 = Total progenies
x = 1 = No. of progenies with blonde hair
y = 2 = No. of progenies with blonde hair
p= 1/4 = Probability of having blonde hair
q = 3/4 = Probability of having brown hair