A recessive allele can persist in a population because some individuals are carriers.

• A. Dominant allele
• B. Carriers exist
• C. New mutation
• D. Random chance

Answer: (B)

A recessive allele can persist because it can be carried by individuals who do not express the trait. When a person has one recessive allele and one dominant allele, they are a carrier and appear normal, yet they can pass the recessive allele to their offspring. If two carriers mate, some children may show the trait, but many will be unaffected carriers themselves, so the allele remains in the population across generations. This hidden reservoir of recessive alleles means the allele can persist even when the phenotype is rarely seen.

The other ideas don’t explain this mechanism as directly. A dominant allele involves a different pattern of expression and doesn’t account for how a recessive allele remains in the gene pool. A new mutation would introduce a new copy but doesn’t address why an existing recessive allele stays around. Random chance can influence frequencies, but it doesn’t describe the ongoing presence of the allele through carriers in the population.