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.
If predation continues, what are the allele frequencies when the second generation mates?

Verified step by step guidance

1. Step 1: Understand the problem. The question involves calculating allele frequencies in the second generation after natural selection has acted on the population. The relative fitness values for each genotype (C₁C₁, C₁C₂, and C₂C₂) are provided, along with the initial allele frequencies f(C₁) = 0.80 and f(C₂) = 0.20.
2. Step 2: Calculate the genotype frequencies before selection. Use the Hardy-Weinberg principle to determine the initial genotype frequencies: f(C₁C₁) = (f(C₁))², f(C₁C₂) = 2 × f(C₁) × f(C₂), and f(C₂C₂) = (f(C₂))². Represent these calculations using MathML: $f^C$₁=fC₁×fC₁.
3. Step 3: Apply the relative fitness values to the genotype frequencies. Multiply each genotype frequency by its respective fitness value to calculate the post-selection genotype frequencies. For example, f'(C₁C₁) = f(C₁C₁) × 0.30, f'(C₁C₂) = f(C₁C₂) × 0.60, and f'(C₂C₂) = f(C₂C₂) × 1.0.
4. Step 4: Normalize the post-selection genotype frequencies. To ensure the frequencies sum to 1, divide each post-selection genotype frequency by the total sum of all post-selection genotype frequencies. Represent this normalization step using MathML: $\mathrm{f\text{'}}C$₁=f'C₁Σ(f'C₁+f'C₂).
5. Step 5: Calculate the allele frequencies in the second generation. Use the normalized genotype frequencies to determine the allele frequencies. For example, f'(C₁) = f'(C₁C₁) + 0.5 × f'(C₁C₂), and f'(C₂) = f'(C₂C₂) + 0.5 × f'(C₁C₂). Represent these calculations using MathML: $\mathrm{f\text{'}}C$₁=f'C₁+12×f'C₁C₂.

Key Concepts

Allele Frequency

Allele frequency refers to how often a particular allele appears in a population relative to the total number of alleles for that gene. It is expressed as a proportion or percentage and is crucial for understanding genetic variation and evolution within a population. In this scenario, the initial frequencies of alleles C₁ and C₂ are given, which will change due to natural selection.

Codominance

Codominance is a genetic scenario where both alleles in a heterozygote are fully expressed, resulting in a phenotype that is a combination of both traits. In this case, the C₁C₂ genotype produces orange flowers, illustrating how codominance can lead to phenotypic diversity in a population. Understanding this concept is essential for predicting how different genotypes will respond to environmental pressures.

Natural Selection

Natural selection is the process by which certain traits become more or less common in a population based on their impact on survival and reproduction. In this example, the predation of yellow and orange flowers leads to differential survival of the flower genotypes, favoring the red flowers (C₂C₂) with higher relative fitness. This concept is fundamental for predicting changes in allele frequencies over generations.