Question

Suppose that a dominant allele (P) codes for a polka-dot tail and a recessive allele (p) codes for a solid colored tail. In addition, suppose that a dominant allele (L) codes for long eyelashes and a recessive allele (l) codes for short eyelashes. If two individuals heterozygous for both traits (tail color and eyelash length) mate, what's the probability of the phenotypic combinations of the offspring?

A. 1:1 ratio (half are polka-dot tails and short eyelashes; half are solid tails and long eyelashes)
B. 9:3:3:1 ratio (9 polka-dot tails and long eyelashes, 3 polka-dot tails and short eyelashes, 3 solid tails and long eyelashes, 1 solid tail and short eyelash)
C. 9:3:3:1 ratio (9 polka-dot tails and short eyelashes, 3 polka-dot tails and long eyelashes, 3 solid tails and short eyelashes, 1 solid tail and long eyelash)
D. 1:1 ratio (half are polka-dot tails and long eyelashes; half are solid tails and short eyelashes)

Answer 1

Written above we have an example of a dihybrid cross. When two individuals that are heterozygous for both of the two traits we are observing cross we expect to get four different phenotypes in the ratio of  9:3:3:1 :
9  dominant for both traits : (polka-dot tails and long eyelashes)
3 dominant for one, recessive for the other (polka-dot tails and short eyelashes) 
3 recessive for the first one, dominant for the other (solid tails and long eyelashes)
1 recessive for both traits (solid tail and short eyelash)