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

Answer 1

C. 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)
Since both parents are heterozygous for both traits, we can create a 4x4 Punnett square with the labels pl, pL, Pl, and PL for each axis, creating 16 possible offspring. They are:
ppll, pplL, ppLl, ppLL, pPll, pPlL, pPLl, pPLL, Ppll, PplL, PpLl, PpLL, PPll,
PPlL, PPLl, and PPLL.
Of those 16 possible offspring, the full gamut of traits are shown in the following numbers:
solid-tail, short eyelashes: 1
solid-tail, long eyelashes: 3
polka-dot-tail, short eyelashes: 3
polka-dot-tail, long eyelashes: 9
And of the available choices, only option "C" matches.