In goats a beard is produced by an autosomalallele that is d

In goats, a beard is produced by an autosomalallele that is dominant in males and recessive in females. If we cross a heterozygous bearded male goat with a heterozygous beardless female goat, what phenotypes would we expect, in what proportions? females 3/4 beardless, 1/4 bearded; males 3/4 bearded, 1/4 beardless all females beardless, all males bearded 3/4 bearded, 1/4 beardless, regardless of sex 1/2 bearded, 1/2 beardless, regardless of sex all females beardless, males 3/4 bearded 1/4 bearded all females beardless, males 1/2 bearded, 1/2 bearded

Solution

Answer is A: females 3/4 beardless, 1/4 bearded; males 3/4 bearded, 1/4 beardless

Beard: B^b

Beardless: B⁺

B^b is dominant in males that is presence of single B^b is enough to produce beard. In females, it is recessive that is two B^b should be present to produce beard.

Cross : Heterozygous bearded male goat x Heterozygous beardless female goat

  B^bB⁺ x        B^bB⁺

     B^b

     B⁺

     B⁺

B^b B⁺

     B⁺ B⁺

     B^b

B^b B^b

     B^b B⁺

B^b B⁺ : 2/4

B⁺ B^{+ :} 1/4

B^b B^{b :} 1/4

Females : 1/4 + 2/4 (B⁺ B⁺ & B^b B⁺ ) = 3 /4 = Beardless and 1/4 (B^b B^b) = Bearded

Males : 2/4 + 1/4 (B⁺B^b & B^b B^b ) = 3/4 = bearded and 1/4 (B⁺ B⁺) = Beardless

So females 3/4 beardless, 1/4 bearded ; males 3/4 bearded, 1/4 beardless

	Bb	B+
B+	Bb B+	B+ B+
Bb	Bb Bb	Bb B+