Humber Admissions Practice Test

What does a genotype of "Aa" indicate about an organism?

1. It has two recessive alleles

2. It has two dominant alleles

3. It is heterozygous

4. It is homozygous recessive

The correct answer is: It is heterozygous

A genotype of "Aa" indicates that the organism is heterozygous. This term describes an organism that has two different alleles for a specific gene—one dominant allele (represented by "A") and one recessive allele (represented by "a"). Heterozygosity is crucial in genetics because it often results in a phenotype that expresses the dominant trait due to the presence of the dominant allele. This characteristic can lead to greater genetic variation within a population, which is important for adaptability and evolution. In contrast, a genotype with two identical alleles, whether dominant or recessive, would be categorized as homozygous, which is not the case here. Thus, understanding the implications of heterozygous genotypes provides insight into inheritance patterns and phenotypic outcomes within the context of genetics.