Question

Assume that in cattle a spotted coat is dominant to an even coat, short horns are dominant to long horns, and the traits for coat type and horn length assort independently. In a cross between cattle that are each heterozygous for both traits, what proportion of their offspring are expected to have long horns?
A) 1/16
B) 3/16
C) 1/4
D) 9/16

Answer 1

Answer:

C. 1/4

Explanation:

Let's assume that the allele for the spotted coat is "S" and the one for the even coat is "s". The allele "L" gives short horns while the recessive allele "l" imparts long horns. The genotype of the cattle heterozygous for both traits would be SsLl. A cross between two heterozygous cattle would produce progeny in following phenotype ratio=

9 spotted coat and short horns: 3 even coat and short horns: 3 spotted coat and long horns: 1 even coat and long horns.

Therefore, the proportion of the progeny with long horns = 4/16= 1/4