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Sourav PanOctober 25, 2024

Calculate the genotype and allele frequencies. What would be the expected genotype frequencies if this population were in genetic equilibrium?

Calculate the genotype and allele frequencies. What would be the expected genotype frequencies if this population were in genetic equilibrium?

Sourav Pan
Sourav PanOctober 25, 2024

Answered step-by-step

Sample Dataset for Demonstration:

Genotype Number of Individuals
AA 80
Aa 60
aa 20
Total 160

1. Calculating Genotype Frequencies

  • Genotype Frequency Formula: (Number of individuals with the genotype) / (Total number of individuals)
Genotype Number of Individuals Genotype Frequency
AA 80 80/160 = 0.5
Aa 60 60/160 = 0.375
aa 20 20/160 = 0.125
Total 160 1.0

2. Calculating Allele Frequencies

  • Allele Frequency Formula: (Number of copies of the allele) / (Total number of alleles)
    • Total Alleles: 2 * Total Individuals = 2 * 160 = 320 alleles
    • Counting Alleles:
      • A Allele in AA: 80 individuals * 2 = 160 A alleles
      • A Allele in Aa: 60 individuals * 1 = 60 A alleles
      • Total A Alleles: 160 + 60 = 220 A alleles
      • a Allele in aa: 20 individuals * 2 = 40 a alleles
      • a Allele in Aa: 60 individuals * 1 = 60 a alleles
      • Total a Alleles: 40 + 60 = 100 a alleles
Allele Number of Copies Allele Frequency
A 220 220/320 = 0.6875
a 100 100/320 = 0.3125
Total 320 1.0

3. Expected Genotype Frequencies under Hardy-Weinberg Equilibrium (HWE)

Given p (A allele frequency) = 0.6875 and q (a allele frequency) = 0.3125, the expected genotype frequencies under HWE are calculated as:

  • Expected Frequency of AA (p^2): (0.6875)^2 = 0.47265625
  • Expected Frequency of Aa (2pq): 2 * 0.6875 * 0.3125 = 0.4296875
  • Expected Frequency of aa (q^2): (0.3125)^2 = 0.09765625
Genotype Observed Frequency Expected HWE Frequency
AA 0.5 0.47265625
Aa 0.375 0.4296875
aa 0.125 0.09765625
Total 1.0 1.0

Comparison:

  • The observed genotype frequencies are somewhat close to the expected frequencies under HWE, suggesting the population might be near equilibrium for this locus. However, to conclusively determine if the population deviates significantly from HWE, statistical tests like Fisher’s exact test (mentioned in your query results) would be necessary.

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