Question

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

Answer 1

The correct answer is B. The parents are heterozygous with polka-dot tails, so they both have Pp genotype. The combination of their genotypes (Pp x Pp) could produce 4 genotypes PP, Pp, Pp and pp. Therefore, there is 25% chance for a PP genotype, 25% for a pp genotype and 50% for a Pp genotype. The PP and Pp genotypes produce a polka-dot tail phenotype and the pp genotype produces a solid coloured tail phenotype. In conclusion, there is 75% chance for a polka-dot tail (25% for a PP + 50% for a Pp) and a 25% for a solid coloured tail phenotype (25% for a pp).