Advanced Placement (AP) Biology Practice Exam

Which of the following describes multiple alleles?

1. A gene with a single allele option

2. A trait influenced by two genes

3. A gene with more than two allele options

4. A dominant and recessive allele combination

The correct answer is: A gene with more than two allele options

The concept of multiple alleles refers to the existence of more than two alternative forms of a gene that can exist at the same locus on a chromosome. Each individual organism typically possesses two alleles for any given gene, inheriting one from each parent; however, the overall population may have several variants, or alleles, available for that gene. This diversity in alleles can lead to variations in traits, as seen in examples like the ABO blood group system, where the A, B, and O alleles all contribute to an individual's blood type. This situation clarifies why the correct answer pertains to a gene that has more than two options, rather than being limited to just one allele, influenced by two genes, or discussing dominant and recessive combinations. Multiple alleles provide a wider array of potential phenotypes and genotypes in a population, enriching genetic diversity.