Which statement accurately describes alleles at a gene locus?

Which statement accurately describes alleles at a gene locus?

• A. Populations may have more than two alleles, but individuals typically have two.
• B. Each individual has four alleles for a gene.
• C. A gene has only one allele in a population.
• D. Alleles are always identical across the population.

Answer: (A)

The key idea is that an individual, being diploid, carries two copies of each gene (one on each homologous chromosome), so they typically have two alleles at a locus. But a population can harbor many different alleles for that same gene due to genetic variation over time. So the statement that populations may have more than two alleles, while individuals usually have two, best captures how alleles are distributed. The other ideas misstate biology: a single individual does not carry four alleles for one gene, a population can have more than one allele, and alleles are not identical across all individuals.

The key idea is that an individual, being diploid, carries two copies of each gene (one on each homologous chromosome), so they typically have two alleles at a locus. But a population can harbor many different alleles for that same gene due to genetic variation over time. So the statement that populations may have more than two alleles, while individuals usually have two, best captures how alleles are distributed. The other ideas misstate biology: a single individual does not carry four alleles for one gene, a population can have more than one allele, and alleles are not identical across all individuals.