In a sample of 1000 adults drawn at random from a mealworm farm, you discover: 657 black beetles, 246 brown beetles, and 97 red beetles.

Question

What are the frequencies for the three genotypes?

what are the allele frequencies?

What are expected genotype frequencies under Hardy-Weinberg?

What is the the deviation (if there is any) from the non-evolving population and what you can infer about the evolutionary status of the population?

Is there is proof that this population is developing, what are two explanations for the observed departure from Hardy-Weinberg, one using natural selection and the other involving nonrandom mating?

Answer 1

Calculations:

1. Genotype Frequencies:
2. BB genotype: 657/1000 = 0.657 (frequency)
3. Bb genotype: 246/1000 = 0.246 (frequency)
4. bb genotype: 97/1000 = 0.097 (frequency)
5. Allele Frequencies:

p is the frequency of the dominant allele - BB + (0.5*Bb)

q is the frequency of the recessive allele - bb + (0.5*Bb)



1. The allele frequencies can be calculated from the genotype frequencies.
2. The frequency of the "B" allele (p) is the sum of the frequencies of the BB and half of the Bb individuals since each heterozygous individual contributes one "B" allele.
3. p = (0.657 + 0.5 * 0.246) = 0.657 + 0.123 = 0.780
4. The frequency of the "b" allele (q) is similarly calculated:
5. q = (0.097 + 0.5 * 0.246) = 0.097 + 0.123 = 0.220
6. Expected Genotype Frequencies under Hardy-Weinberg:
7. The expected genotype frequencies under Hardy-Weinberg can be calculated using the allele frequencies:
8. Frequency of BB genotype (p^2) = p * p = (0.780 * 0.780) = 0.608
9. Frequency of Bb genotype (2pq) = 2 * p * q = 2 * 0.780 * 0.220 = 0.344
10. Frequency of bb genotype (q^2) = q * q = (0.220 * 0.220) = 0.048
11. Deviations from Hardy-Weinberg:
12. To determine if there is a deviation from the Hardy-Weinberg equilibrium, compare the observed genotype frequencies with the expected genotype frequencies.
13. Observed BB frequency: 0.657
14. Observed Bb frequency: 0.246
15. Observed bb frequency: 0.097
16. Expected BB frequency: 0.608
17. Expected Bb frequency: 0.344
18. Expected bb frequency: 0.048
19. The observed frequencies deviate slightly from the expected frequencies, suggesting a departure from Hardy-Weinberg equilibrium.
20. Possible Explanations for Deviation:
21. Natural Selection: If certain genotypes have a higher fitness in the environment (e.g., black beetles are better camouflaged), natural selection may favor those genotypes, leading to a departure from Hardy-Weinberg equilibrium.
22. Nonrandom Mating: If individuals tend to mate with those of the same color (assortative mating), it can lead to an excess of homozygous individuals (BB and bb) and a deficit of heterozygous individuals (Bb), causing a departure from Hardy-Weinberg equilibrium.

The observed departure from Hardy-Weinberg equilibrium suggests that evolutionary forces, such as natural selection or nonrandom mating, may be at play in this population of beetles. Further investigations would be needed to determine the exact cause of the deviation and its implications for the population's evolutionary status.