Final answer:
Heterozygosity is beneficial due to heterozygote advantage, where individuals who are heterozygous have a higher fitness. This allows them to benefit from the advantages of both alleles. For example, in sickle cell anemia, heterozygotes have a selective advantage in regions with malaria.
Step-by-step explanation:
The evidence that suggests heterozygosity is beneficial is known as heterozygote advantage or overdominance. In this condition, individuals who are heterozygous (having two different alleles) have a higher fitness than individuals who are homozygous for either allele. This is because heterozygotes can benefit from the advantages of both alleles, such as resistance to diseases or improved metabolism.
For example, sickle cell anemia is a genetic disorder caused by a recessive allele. However, individuals who are heterozygous for this allele have a selective advantage in regions where malaria is prevalent. They are less susceptible to malaria while still avoiding the severe symptoms of sickle cell anemia.
In the case of sickle cell anemia, the value of 2pq would increase in a population undergoing heterozygote advantage. This is because heterozygotes have a higher fitness and are more likely to pass on their alleles to the next generation, increasing the frequency of the heterozygous genotype in the population.