Question

If a trait is solely determined by additive genetic variance, what phenotypes would be expected for the given genotypes: aa, Aa, AA?

a) aa: intermediate phenotype, Aa: dominant phenotype, AA: recessive phenotype.
b) aa: recessive phenotype, Aa: intermediate phenotype, AA: dominant phenotype.
c) aa: dominant phenotype, Aa: intermediate phenotype, AA: recessive phenotype.
d) aa: intermediate phenotype, Aa: recessive phenotype, AA: dominant phenotype.

Answer 1

When a trait is determined by additive genetic variance, the genotypes aa, Aa, and AA will result in recessive, intermediate, and dominant phenotypes, respectively, following the principles of quantitative genetics.

Step-by-step explanation:

If a trait is solely determined by additive genetic variance, the phenotypes expected for the given genotypes would be influenced by the effect of both alleles adding up to create the phenotype. In this situation, the genotypes aa, Aa, and AA would yield specific phenotypes:

• aa: Homozygous recessive genotype, expressing the recessive phenotype.
• Aa: Heterozygous genotype, expressing an intermediate phenotype.
• AA: Homozygous dominant genotype, expressing the dominant phenotype.

This pattern of inheritance follows the quantitative genetics approach where the effects of alleles are cumulative. Therefore, the correct answer to the student's question is b) aa: recessive phenotype, Aa: intermediate phenotype, AA: dominant phenotype.