Question

How might a mutant allele that causes an inherited illness in homozygotes persist in a population?

Short answer

A mutant allele causing an inherited illness in homozygotes can persist in a population due to the heterozygote advantage. Carriers of the mutation (heterozygotes) sometimes have increased survival or reproduction rates, allowing them to pass on the mutant allele to the next generation.

Step-by-step solution

Understanding the Basics

Different alleles can exist for single genes. These alleles may be dominant or recessive, with a mutation that is harmful usually being a recessive trait. Individuals with a recessive mutant allele paired with a normal or dominant allele, in other words, heterozygotes, are typically carriers, showing no signs of the illness.

Exploring the Heterozygote Advantage

In some cases, being a carrier or heterozygote for a certain mutation can bring about a benefit in certain environments or conditions, a phenomenon known as the heterozygote advantage. This advantage can lead to an increased rate of survival or reproduction.

Determining the Persistence of the Mutant Allele

Because carriers possess certain advantages due to heterozygote advantage, they live to reproduce and pass along the mutation to their offspring, even though a homozygous pair of the allele results in illness. In this way, the mutant allele can persist in the population.