Which of the following would you NOT expect to see from a population that has experienced genetic drift?

Question

BlackTom AI · Accepted Answer

Genetic drift causes random changes in allele frequencies, tending to reduce genetic variation over time—especially in small or isolated populations.

1) Relevant knowledge points and concepts
- Genetic drift: stochastic fluctuation in allele frequencies from one generation to the next, independent of fitness.  
- Effects: loss of alleles, increased chance of fixation or loss, reduced heterozygosity (genetic diversity).  
- Drift is strongest when effective population size (Ne) is small or when populations are isolated (limited gene flow). Bottlenecks and founder effects are classic drift scenarios.

2) Step-by-step reasoning
- If drift acts, allele frequencies move randomly; neutral alleles can become fixed or lost.  
- Fixation/loss reduces the number of alleles and heterozygosity in the gene pool.  
- Small population size → larger sampling error each generation → stronger drift.  
- Low immigration (isolation) prevents introduction of new alleles, so drift’s reductive effect is not countered by gene flow.

3) Calculations / intermediate steps (heterozygosity change example)
- Expected heterozygosity after one generation: H1 = H0 (1 - 1/(2Ne)).  
- Example: Ne = 50 → factor = 1 - 1/(2×50) = 1 - 1/100 = 0.99, so H1 = 0.99 H0 (a 1% loss per generation). Over many generations this compounds, showing substantial loss of diversity.

4) Why the correct answer is correct
- High levels of genetic diversity are not expected under genetic drift because drift tends to remove alleles and lower heterozygosity. Therefore, observing high genetic diversity would be inconsistent with having experienced strong genetic drift.

5) Why the other options are incorrect
- B) Small population size: expected, because drift is stronger in small populations.  
- C) Low levels of genetic diversity: expected outcome of drift.  
- D) Isolated population with low immigration: expected, since lack of gene flow allows drift to dominate.  
- E) “All will be expected”: incorrect because A (high diversity) is not expected.

6) Conclusion
High levels of genetic diversity would NOT be expected after genetic drift; therefore the correct choice is A) high levels of genetic diversity, matching the provided answer.

Which of the following would you NOT expect to see from a population that has experienced genetic drift?单项选择题

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