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. 1:1 ratio (half are polka-dot tails and long eyelashes; half are solid tails and short eyelashes)  
D. 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)

Answer 1

A. 9:3:3:1 ratio (9 polka-dot tails and long eyelashes, 3 polka-dot tails and short eyelashes, 3 solid tails and short eyelashes, 1 solid tail and short eyelash)

As a rule in a dihybrid cross the ratios is always 9:3:3:1 with 1 having the recessive combination and 9 being the Dominant combination.

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Answer 2

This is a di-hybrid problem. When doing a punnet square for di-hybrid problems, I would suggest using the F.O.I.L method to determine how to place the alleles.

Since both individuals are heterozygous, they will be both PpLl x PpLl.

By doing the punnet square, I get the answer of D.