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9. 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 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 long eyelashes; half are solid tails and short eyelashes)

Respuesta :

The answer to this question should be: 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) 

In this question, there are 4 kinds of alleles that will interact. To answer this question, it might be easier to make a table of the probability.
Since both of the parents is heterozygous, that means both of them have 4 different possible alleles that can be inherited. That will makes the table become 4x4 table resulting 16 cells. In those 16 cells, 9 cell will have both dominant allele, 3 dominant + recessive allele, 3 recesive+ dominant alleles and 1 will be both recessive alleles. (remember that you only need 1 dominant allele to be expressed as dominant, but need 2 alleles to express the recessive)

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