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A single gene mutation in cats can result in curly ears (see image). The cats are healthy and normal beyond the ear structure. The curly ear trait is recessive, and the allele for curly ears is $ and the allele for regular ears is S. Select the best response from the options below. a A - the phenotype for S$ is curly ears b B - the phenotype for $$ is curly ears c C - the genotype S$ results in a cat with regular ears d D - the phenotype SS results in a deadly genotype e F - B and C are correct

1 answer

To determine the best response, let's break down the genetic information given:

  • The curly ear trait (allele $) is recessive.
  • The allele for regular ears is S, which is dominant over the curly ear allele.

  1. Genotype Analysis:

    • SS: This genotype will produce regular ears (since S is dominant).
    • S$: This genotype will also produce regular ears because the presence of the dominant S allele masks the effect of the recessive $ allele.
    • $$: This genotype will produce curly ears since there are two recessive alleles present.

  2. Phenotypes based on genotypes:

    • Phenotype for SS: Regular ears.
    • Phenotype for S$: Regular ears.
    • Phenotype for $$: Curly ears.

Now, let's evaluate the statements:

a. A - the phenotype for S$ is curly ears: This is incorrect. The phenotype for S$ is regular ears.

b. B - the phenotype for $$ is curly ears: This is correct. The phenotype for $$ is indeed curly ears.

c. C - the genotype S$ results in a cat with regular ears: This is correct. The S$ genotype has regular ears due to the presence of the dominant allele S.

d. D - the phenotype SS results in a deadly genotype: This is incorrect. There is no indication in the information provided that SS is a deadly genotype.

e. F - B and C are correct: Since both B and C are correct, this is indeed a valid response.

Given this analysis, the best response is:

F - B and C are correct.