In cocker spaniels, solid coat color is dominant over spotted coat color. If two

Question

In cocker spaniels, solid coat color is dominant over spotted coat color. If two heterozygous dogs were crossed to each other, what would be the probability of the following combinations of offspring?

a. A litter of eight pups, two with solid fur and six with spotted fur.

b. A first litter of six pups, four with solid fur and two with spotted fur, and then a second litter of five pups, all with solid fur.

c. A first litter of five pups, the firstborn with solid fur, and then among the next four, three with solid fur and one with spotted fur, and then a second litter of seven pups in which the firstborn is spotted, the second born is spotted, and the remaining five are composed of four solid pups and one spotted pup.

use binominal expansion please

Explanation / Answer

Let the allel for solid coor be S and for spotted coat color be s

Ss x Ss

S s

S SS Ss

s Ss ss

a) the proportion of spotted fur is 1/4

the proportion for solid fur is 3/4

Binomial expansion theorem : n!/x!(n-x)! (p)x (q)n-x

8!/6!2!(1/4)6 (3/4)2

8x7x6!/6!x2(1/4)6 (3/4)2

56/2 (0.00024) (0.56) =0.00378

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