Question

Suppose two plant populations exchange pollen and seeds. In one population, individuals of genotype AA are most common (9,000 AA, 900 Aa, 100 aa), while the opposite is true in the other population (100 AA, 900 Aa, 9,000 aa). If neither allele has a selective advantage, what will happen over time to the allele and genotype frequencies of these populations?

Short answer

The population is not small in the given case. Therefore, it does not matter when alleles do not have a selective advantage at the locus. Pollen grains and seeds are exchanged between two populations, which leads to gene flow between them.

Since the population is large, it takes much time to have similar gene frequencies. The two populations will have similar genotypes over time due to gene flow.

Step-by-step solution

Genotype frequency

Genotype frequency is obtained by dividing the number of individuals in a genotype by the total number of individuals in a population.It is used in analyzing the variations in a population and diagnosing genetic disorders.

Gene frequency is calculated by using the Hardy-Weinberg equation $p^2+2pq+q^2$. Here, p² denotes dominant homozygous frequency, and q² denotes recessive homozygous frequency. Moreover, 2pq represents the frequency of heterozygous alleles.

Selective advantage

The force of natural selection enhances the characteristic or trait that gives better survival adaptations by increasing their relative fitness. This is called selective advantage.

Selective advantage produced by genes provides an organism with the ability to compete for food, protect itself from predators, or resist diseases.

Gene flow between two different populations

When pollen grains are exchanged, or interbreeding occurs between two different populations, gene flow occurs.It is one of the evolutionary forces that enable an organism to develop new traits.

In the given case, even though interbreeding occurs, neither populations show selective advantage due to the large size.

Therefore, the frequencies of the alleles in both populations become more similar over time. The effects of genetic drift do not apply to the large population.