What happens when we change the gene frequency in a population?

What happens when we change the gene frequency in a population?

• A. We change the mean and move the population in a desired direction
• B. We randomize genotype frequencies
• C. We decrease heterozygosity
• D. We have no effect on phenotype

Answer: (C)

When allele frequencies in a population shift, the genetic variation at that locus changes accordingly. For a simple two-allele locus, heterozygosity is given by 2pq (where p and q are the allele frequencies and p + q = 1). Heterozygosity is highest when p is 0.5 and decreases as p moves toward 0 or 1. So, when selection or other forces push the population toward one favored allele, the allele frequencies move away from balance and heterozygosity declines. If one allele becomes fixed (p = 1 or p = 0), heterozygosity drops to zero. This is why changing gene frequency often reduces heterozygosity. Phenotype can change with allele frequency changes, and genotype frequencies under random mating follow HW expectations (not a randomization). The idea that there would be no effect on phenotype or that genotype frequencies become randomized isn’t generally correct, whereas the decline in heterozygosity directly reflects the shift toward fixation.

When allele frequencies in a population shift, the genetic variation at that locus changes accordingly. For a simple two-allele locus, heterozygosity is given by 2pq (where p and q are the allele frequencies and p + q = 1). Heterozygosity is highest when p is 0.5 and decreases as p moves toward 0 or 1. So, when selection or other forces push the population toward one favored allele, the allele frequencies move away from balance and heterozygosity declines. If one allele becomes fixed (p = 1 or p = 0), heterozygosity drops to zero. This is why changing gene frequency often reduces heterozygosity.

Phenotype can change with allele frequency changes, and genotype frequencies under random mating follow HW expectations (not a randomization). The idea that there would be no effect on phenotype or that genotype frequencies become randomized isn’t generally correct, whereas the decline in heterozygosity directly reflects the shift toward fixation.