What hypothesis best explains the observation of a rare purple plumed parrot crossed with a white parrot yielding 1/2 white and 1/2 purple parrots?

What hypothesis best explains the observation of a rare purple plumed parrot crossed with a white parrot yielding 1/2 white and 1/2 purple parrots?

• A. The white allele is incompletely dominant
• B. The purple allele is lethal in the homozygous state
• C. Both parental alleles are recessive
• D. The color is determined by two separate genes

Answer: (B)

The scenario presents a classic example of Mendelian inheritance, where the outcome of a cross between a purple plumed parrot and a white parrot results in a ratio of 1/2 white and 1/2 purple parrots. The hypothesis that best explains this observation is that the purple allele is lethal in the homozygous state. In this case, when the purple plumed parrot, which we can assume has a genotype of homozygous purple (PP), is crossed with a white parrot, which is likely homozygous white (pp), the offspring could inherit various combinations of these alleles. The expectation is that the offspring could be either PP or pp. However, if the purple allele (P) is lethal when homozygous, any offspring receiving the PP genotype would not survive, resulting in a lower-than-expected number of purple individuals. As a result, among the surviving offspring, we would see a 1:1 ratio of white (pp) to purple (Pp) parrots, since the only viable combinations are the heterozygous purple (Pp) and the homozygous white (pp). The lethal nature of the homozygous purple genotype explains why there are no viable

The scenario presents a classic example of Mendelian inheritance, where the outcome of a cross between a purple plumed parrot and a white parrot results in a ratio of 1/2 white and 1/2 purple parrots. The hypothesis that best explains this observation is that the purple allele is lethal in the homozygous state.

In this case, when the purple plumed parrot, which we can assume has a genotype of homozygous purple (PP), is crossed with a white parrot, which is likely homozygous white (pp), the offspring could inherit various combinations of these alleles. The expectation is that the offspring could be either PP or pp. However, if the purple allele (P) is lethal when homozygous, any offspring receiving the PP genotype would not survive, resulting in a lower-than-expected number of purple individuals.

As a result, among the surviving offspring, we would see a 1:1 ratio of white (pp) to purple (Pp) parrots, since the only viable combinations are the heterozygous purple (Pp) and the homozygous white (pp). The lethal nature of the homozygous purple genotype explains why there are no viable