Multiple Choice
In genetics, when using letter symbols to represent alleles, how is a dominant allele typically represented?
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3. Extensions to Mendelian Inheritance
Variations of Dominance
Multiple Choice
In the context of variations of dominance, what best defines a recessive allele?
A
An allele that is always expressed whenever it is present, even in a heterozygote
B
An allele whose phenotype is masked in a heterozygote by a dominant allele and typically expressed only in a homozygote
C
An allele that is expressed only in males because it is located on the chromosome
D
An allele that produces an intermediate (blended) phenotype in heterozygotes due to incomplete dominance
Verified step by step guidance1
Understand the concept of dominance in genetics, which describes how different alleles interact to produce a phenotype in heterozygotes.
Recall that a recessive allele is one whose effect on the phenotype is not observed when paired with a dominant allele in a heterozygous individual.
Recognize that the phenotype associated with a recessive allele is typically only visible when the organism is homozygous for that allele (i.e., has two copies of the recessive allele).
Note that dominant alleles mask the expression of recessive alleles in heterozygotes, meaning the dominant trait is expressed instead.
Therefore, the best definition of a recessive allele is: an allele whose phenotype is masked in a heterozygote by a dominant allele and typically expressed only in a homozygote.
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