yannelle98
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Suppose that a dominant allele (P) codes for a polka-dot tail and a recessive allele (p) codes for a solid colored tail. If two heterozygous individuals with polka-dot tails mate, what's the probability of the phenotype and genotype combinations of the offspring?

A. 25 percent chance of a polka-dot tail and 75 percent chance of a solid colored tail (25 percent PP; 50 percent Pp; 25 percent pp)
B. 75 percent chance of a polka-dot tail and 25 percent chance of a solid colored tail (25 percent PP; 50 percent Pp; 25 percent pp)
C. 75 percent chance of a polka-dot tail and 25 percent chance of a solid colored tail (75 percent Pp; 25 percent pp)
D. 50 percent chance of a polka-dot tail and 50 percent chance of a solid colored tail (50 percent PP; 50 percent pp)

Respuesta :

JcAlmighty
The answer is B. 75 percent chance of a polka-dot tail and 25 percent chance of a solid colored tail (25 percent PP; 50 percent Pp; 25 percent pp) 

If P represents dominant allele (a polka-dot tail), p represents recessive allele (a solid colored tail), then heterozygous individuals have Pp genotype. All alleles will combine each other:

Parental generation:      Pp     x     Pp
Offspring:                  PP    Pp    Pp    pp

Thus, the probability of PP genotype is 1/4 (there is only 1 of total 4 possible genotypes), which is 25%. The probability of Pp genotype is 1/2 or 50%, and the probability of pp genotype is 1/2 or 25%.

Talking of phenotypes, the P allele is dominant and each genotype containing P allele will have the polka-dot phenotype. In this case, there are 3 out of 4 genotypes containing P allele - 1 PP and 2 Pp. So, the probability of the polka-dot tail is 3/4 or 75%, leaving the probability of the solid color tail 1/4 or 25%.