In a population of flowers growing in a meadow, C₁ and C₂ are autosomal codominant alleles that control flower color. The alleles are polymorphic in the population, with f(C₁) = 0.80 and f(C₂) = 0.20. Flowers that are C₁C₁ are yellow, orange flowers are C₁C₂, and C₂C₂ flowers are red. A storm blows a new species of hungry insects into the meadow, and they begin to eat yellow and orange flowers but not red flowers. The predation exerts strong natural selection on the flower population, resulting in relative fitness values of C₁C₁ = 0.30, C₁C₂ = 0.60, and C₂C₂ = 1.0.
Assuming the population begins in H-W equilibrium, what are the allele frequencies after one generation of natural selection?

Verified step by step guidance

1. Step 1: Begin by recalling the Hardy-Weinberg equilibrium principle, which states that allele frequencies in a population remain constant from generation to generation in the absence of evolutionary forces. However, in this case, natural selection is acting on the population, so we need to calculate the new allele frequencies after selection.
2. Step 2: Write down the initial allele frequencies: f(C₁) = 0.80 and f(C₂) = 0.20. Use these to calculate the genotype frequencies under Hardy-Weinberg equilibrium. The genotype frequencies are: f(C₁C₁) = (f(C₁))², f(C₁C₂) = 2 × f(C₁) × f(C₂), and f(C₂C₂) = (f(C₂))².
3. Step 3: Multiply each genotype frequency by its relative fitness value to account for the effects of natural selection. The relative fitness values are given as: w(C₁C₁) = 0.30, w(C₁C₂) = 0.60, and w(C₂C₂) = 1.0. This gives the weighted genotype frequencies: f'(C₁C₁) = f(C₁C₁) × w(C₁C₁), f'(C₁C₂) = f(C₁C₂) × w(C₁C₂), and f'(C₂C₂) = f(C₂C₂) × w(C₂C₂).
4. Step 4: Normalize the weighted genotype frequencies to ensure they sum to 1. This is done by dividing each weighted genotype frequency by the total sum of all weighted genotype frequencies: f'(C₁C₁) / (f'(C₁C₁) + f'(C₁C₂) + f'(C₂C₂)), f'(C₁C₂) / (f'(C₁C₁) + f'(C₁C₂) + f'(C₂C₂)), and f'(C₂C₂) / (f'(C₁C₁) + f'(C₁C₂) + f'(C₂C₂)).
5. Step 5: Calculate the new allele frequencies after selection. The frequency of allele C₁ is given by: f(C₁) = f'(C₁C₁) + 0.5 × f'(C₁C₂), and the frequency of allele C₂ is given by: f(C₂) = f'(C₂C₂) + 0.5 × f'(C₁C₂). These are the allele frequencies after one generation of natural selection.

Key Concepts

Codominance

Codominance is a genetic scenario where two different alleles at a locus are both expressed in the phenotype of a heterozygote. In this case, the alleles C1 and C2 produce distinct flower colors when present together (C1C2 results in orange flowers), allowing for a clear understanding of how these alleles interact and contribute to the overall phenotype in the population.

Natural Selection

Natural selection is a fundamental mechanism of evolution where individuals with traits better suited to their environment tend to survive and reproduce more than those with less advantageous traits. In this scenario, the predation of yellow and orange flowers by insects leads to differential survival based on flower color, impacting the allele frequencies in the next generation.

Hardy-Weinberg Equilibrium

Hardy-Weinberg equilibrium describes a theoretical state in a population where allele frequencies remain constant from generation to generation in the absence of evolutionary influences. This concept provides a baseline to compare against after natural selection occurs, allowing for the calculation of new allele frequencies based on the relative fitness of the genotypes in the population.