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? 1/16 3/16 1/4 9/16

Answer 1

The correct answer is: 1/4

If we name the gene for coat type as A:

a spotted coat can have genotype Aa or AA, while even coat has aa genotype.

If we name the gene for the horn length as B, then short horns have genotype Bb or BB while long horns have bb genotype.

If we cross cattle that are each heterozygous for both traits:

P: AaBb x AaBb

Since they assort independently, the chance of getting an b allele and b allele is 1/2 x 1/2= 1/4