High School

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------------------------------------------------ Predict how allele frequencies (G and g) and phenotype frequencies (green and brown) might change over the next two generations.

Answer :

To predict how allele frequencies (G and g) and phenotype frequencies (green and brown) might change over the next two generations, we need to understand the principles of genetics and the Hardy-Weinberg principle.

Step 1: Understanding Alleles and Phenotypes

  1. Alleles: G and g represent different versions of a gene. In this context, let's assume:

    • G is the allele for a dominant trait (e.g., green color).
    • g is the allele for a recessive trait (e.g., brown color).

  2. Phenotypes: The visible traits. Assuming simple Mendelian genetics:

    • Individuals with GG or Gg genotype will have the green phenotype.
    • Individuals with gg genotype will have the brown phenotype.

Step 2: Applying the Hardy-Weinberg Principle

The Hardy-Weinberg principle helps predict how allele frequencies remain constant from one generation to the next unless certain factors cause them to change. This model assumes:

  • Large population size
  • Random mating
  • No mutation
  • No migration
  • No natural selection

Step 3: Understanding Allele Frequency Changes

  1. Initial Frequencies: Let’s assume:

    • p = frequency of G allele
    • q = frequency of g allele
    • Since p + q = 1, these frequencies add up to 1.

  2. Predicting the Change: Without any external factors, these allele frequencies should remain constant (Hardy-Weinberg equilibrium). However, in real scenarios:

    • Natural Selection might favor one phenotype over another, changing allele frequencies if one color provides a survival advantage.
    • Genetic Drift: In smaller populations, allele frequencies might change randomly across generations.
    • Mutation or Migration can introduce new alleles or alter existing frequencies.

Step 4: Predicting Phenotype Frequencies

  • The frequency of green phenotypes (GG and Gg) can be estimated as p^2 + 2pq.
  • The frequency of brown phenotypes (gg) can be estimated as q^2.

By understanding the underlying factors affecting these frequencies, predictions about how they might change can be more accurate. For an accurate prediction, specific data on selection pressures, population size, and other factors would be necessary.

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