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Question

An isolated population on an island has the following genotypic frequencies:
GenotypeAAAaaa
Frequency0.30.40.3
Assuming that there are only two alleles (A and a) for the gene, the genotypic frequency of AA in the next generation will be ________

This question relates to population genetics and the Hardy-Weinberg equilibrium principle, which predicts genotype frequencies in the next generation based on current allele frequencies, assuming random mating and no evolutionary influences.

Calculating Allele Frequencies

First, determine the frequencies of the alleles 'A' (p) and 'a' (q) from the given genotypic frequencies:

  • Frequency(AA) = 0.3
  • Frequency(Aa) = 0.4
  • Frequency(aa) = 0.3

The allele frequency 'p' (frequency of A) is calculated as:

$ p = \text{Frequency(AA)} + \frac{1}{2} \times \text{Frequency(Aa)} $

Substituting the values:

$ p = 0.3 + \frac{1}{2} \times 0.4 = 0.3 + 0.2 = 0.5 $

The allele frequency 'q' (frequency of a) is calculated as:

$ q = \text{Frequency(aa)} + \frac{1}{2} \times \text{Frequency(Aa)} $

Substituting the values:

$ q = 0.3 + \frac{1}{2} \times 0.4 = 0.3 + 0.2 = 0.5 $

Note: Check that p + q = 1. Here, 0.5 + 0.5 = 1, confirming the allele frequencies.

Predicting Next Generation Genotypic Frequency

Under Hardy-Weinberg assumptions (including random mating), the genotype frequencies in the next generation are determined by the square of the allele frequencies.

The expected genotypic frequency of AA in the next generation is calculated using the formula:

$ \text{Frequency(AA)}_{\text{next gen}} = p^2 $

Using the calculated allele frequency p = 0.5:

$ \text{Frequency(AA)}_{\text{next gen}} = (0.5)^2 = 0.25 $

Therefore, the genotypic frequency of AA in the next generation is expected to be 0.25.

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Important Questions from Population Genetics and Epigenetics

  1. Which of the following conditions will contribute to the stability of a gene pool in a natural population? 

    P. Large population 

    Q. No net mutation 

    R. Non-random mating 

    S. No selection

  2. In a random mating population, $Y$ and $y$ are dominant and recessive alleles, respectively. If the frequency of $Y$ allele in both sperm and egg is $0.70$, then the frequency of $Y/y$ heterozygotes (rounded off to two decimal places) is ________
  3. In a genetic study, $80$ people were found to have alleles for polydactyly. Only $36$ of them were polydactylous. What is the extent of penetrance percentage? _______________

  4. If an unbiased coin is tossed 10 times, the probability that all outcomes are same will be _________ $x10^{-5}$
  5. Consider a population of $10,000$ individuals, of which $2500$ are homozygotes (PP) and $3000$ are heterozygotes (Pp) genotype. The frequency of allele p in the population is _________.
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