Question
Tail length in a certain breed of dog shows incomplete dominance. The Punnett square shows the result of a cross between two dogs with medium-length tails (Tt). In this breed, the allele for long tails (T) is dominant and the allele for short tails ( t ) is recessive. What is the probability of offspring expressing the same tail length trait as the parents? (a) 1 out of 4 (b) 2 out of 4 (c) 3 out of 4 (d) 4 out of 4
Answer
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Answer
#ExplanationThe Punnett square given shows the possible genotypes of the offspring from a cross between two dogs with medium-length tails (Tt). The possible genotypes are TT, Tt, Tt, and tt. In this breed of dog, tail length shows incomplete dominance, which means that the heterozygous genotype (Tt) results in a phenotype that is an intermediate of the two homozygous phenotypes. Therefore, the TT genotype would result in a long tail, the tt genotype would result in a short tail, and the Tt genotype would result in a medium-length tail.The question asks for the probability of the offspring expressing the same tail length trait as the parents, which is a medium-length tail. This trait is expressed by the Tt genotype. Looking at the Punnett square, we can see that there are two Tt genotypes out of a total of four possible genotypes. #AnswerTherefore, the probability of the offspring expressing the same tail length trait as the parents is (b) 2 out of 4.