Multiple Choice
Topic: Variations of Dominance. In a heterozygous individual (Aa), the allele whose phenotype is observed under complete dominance is called the:
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3. Extensions to Mendelian Inheritance
Variations of Dominance
Multiple Choice
In the context of variations of dominance, which statement best defines a dominant allele?
A
An allele that produces an intermediate phenotype only when paired with a different allele.
B
An allele that is expressed only when two identical copies are present in a homozygote.
C
An allele whose phenotype is expressed in a heterozygote, masking the effect of the other allele at the same locus.
D
An allele that is always the most common in a population regardless of its phenotypic effect.
Verified step by step guidance1
Understand the concept of dominance in genetics: dominance refers to the relationship between alleles of a gene, where one allele can mask or suppress the expression of another allele at the same locus.
Recall that a dominant allele is typically defined by its ability to express its phenotype in the presence of a different allele (heterozygous condition), meaning it 'masks' the effect of the recessive allele.
Consider the alternative definitions given: an allele producing an intermediate phenotype in heterozygotes describes incomplete dominance, not dominance; an allele expressed only in homozygotes describes a recessive allele; and allele frequency in a population is unrelated to dominance.
Focus on the key phrase that a dominant allele's phenotype is expressed in a heterozygote and masks the effect of the other allele, which aligns with the classical definition of dominance.
Summarize that the correct definition of a dominant allele is one whose phenotype is expressed in heterozygotes, effectively masking the presence of the other allele at the same locus.
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