Which allele combination represents a recessive monohybrid trait? Multiple Choice Aa aa AA Ab ab
The Correct Answer and Explanation is:
The correct answer is aa.
Explanation:
In genetics, a monohybrid cross involves studying the inheritance of a single trait, which is controlled by a single gene. Each gene has two alleles, one inherited from each parent. These alleles can either be dominant or recessive.
- Dominant alleles are represented by uppercase letters (e.g., A) and will mask the expression of the recessive allele when present.
- Recessive alleles are represented by lowercase letters (e.g., a) and are only expressed when two copies of the recessive allele are present (homozygous recessive).
Now let’s break down the options:
- Aa: This represents a heterozygous genotype, where one dominant allele (A) and one recessive allele (a) are present. Since the dominant allele (A) masks the effect of the recessive allele (a), this individual will display the dominant trait, not the recessive one.
- aa: This represents a homozygous recessive genotype, meaning both alleles are recessive. Since there is no dominant allele to mask the recessive trait, this individual will express the recessive trait.
- AA: This represents a homozygous dominant genotype, where both alleles are dominant. Individuals with this genotype will display the dominant trait.
- Ab: This combination doesn’t apply because it mixes two different alleles that are unrelated to the same gene. In a monohybrid cross, the alleles must correspond to the same trait (e.g., A and a, not A and b).
Therefore, aa is the combination that represents a recessive monohybrid trait, as it expresses the recessive phenotype when two copies of the recessive allele are inherited.
