Final answer:
Heterozygotes can gain benefits through mechanisms such as enhanced gene function, combined advantageous traits, and disease resistance, all of which can increase their survival and reproductive success.
Step-by-step explanation:
Three common ways heterozygotes gain benefits through overdominance include enhanced function of gene products, combined phenotypic advantages, and resistance to diseases.
- Enhanced gene function: A mutant allele may enhance the function of the wild-type gene product, conferring an advantage to the heterozygote. For example, the Antennapedia mutation in Drosophila increases the distribution of gene products, leading to heterozygotes with legs on their heads where antennae should be.
- Combined phenotypic traits: In cases like codominance, both alleles are expressed, giving the heterozygote a combination of traits that can lead to a survival advantage. An example is the human MN blood group, where both M and N antigens are equally expressed.
- Disease resistance: Heterozygotes often have an advantage in resisting diseases. For example, individuals heterozygous for the sickle cell allele are resistant to malaria, which is advantageous in regions where malaria is endemic.
In these scenarios, heterozygotes may be more likely to survive and reproduce, potentially increasing the frequency of the heterozygous genotype (represented by the term 2pq in population genetics) in a population undergoing heterozygote advantage. However, this representation simplifies the complex nature of genetic interactions and should be considered with other factors that influence genetic diversity.