Which of the following is a factor that, by itself, is least likely to promote widespread changes in allele or genotype frequencies in a large population? 单项选择题
A
New mutation
B
Natural selection
C
Directional selection
D
Genetic drift

Question

Which of the following is a factor that, by itself, is least likely to promote widespread changes in allele or genotype frequencies in a large population?

BlackTom AI · Accepted Answer

Genetic drift causes random fluctuations in allele frequencies whose magnitude is inversely related to population size, so in a large population its per-generation effect is minimal.

1) Relevant knowledge points and concepts
- Genetic drift: stochastic change in allele frequencies due to sampling error; stronger in small populations, weaker in large populations. The variance in allele frequency change per generation ≈ p(1−p)/(2Ne), where Ne is the effective population size.
- New mutation: introduces novel alleles; although each mutation is rare, cumulative input across many loci and generations can change allele frequencies.
- Natural selection (including directional selection): nonrandom differential survival/reproduction that systematically increases or decreases allele frequencies; can produce rapid and widespread changes in large populations.
- Directional selection: a form of natural selection that consistently favors one allele or phenotype, driving allele frequency change.

2) Step-by-step reasoning
- Compare the mechanisms by their expected impact in a large population. Selection acts deterministically (on average) and can quickly shift frequencies if selective coefficients are nonzero. Mutations constantly add new alleles (at low per-site rates), which can spread if advantageous. Drift is random and its effect size scales as 1/Ne.

3) Calculations / intermediate steps (illustrative)
- Take Ne = 1,000 and allele frequency p = 0.5. Variance in frequency change ≈ p(1−p)/(2Ne) = 0.25/(2,000) = 0.000125. Standard deviation ≈ sqrt(0.000125) ≈ 0.011 (about a 1.1% fluctuation per generation). Such small fluctuations accumulate slowly and are unlikely to cause widespread allele-frequency shifts by themselves in large populations.
- For Ne = 10, drift variance would be 0.25/(20) = 0.0125, SD ≈ 0.112 (11%), showing much larger impact in small populations.

4) Why the correct answer is correct
- Because genetic drift’s impact decreases as population size increases, in a large population drift alone is least likely to produce widespread, systematic changes in allele or genotype frequencies compared with mutation input or natural/directional selection.

5) Why the other options are incorrect
- New mutation: even though each mutation is rare, continual mutation introduces new alleles that can alter frequencies over time and provide material for selection.
- Natural selection: directly changes allele frequencies by differential fitness and can be strong in large populations.
- Directional selection: a specific form of natural selection that predictably pushes allele frequencies in one direction, producing widespread changes.

6) Conclusion
- Therefore, genetic drift is the factor least likely by itself to promote widespread changes in allele/genotype frequencies in a large population, confirming the provided answer: Genetic drift.

Which of the following is a factor that, by itself, is least likely to promote widespread changes in allele or genotype frequencies in a large population? 单项选择题

类似问题

A population geneticist is studying a population of pea aphids and wants to determine whether the proportion p of aphids that are resistant to a particular insecticide is less than 0.40, the proportion reported in a previous study. Which pair of hypotheses is appropriate for this test?

In natural populations, most genes are

Which of the following is a factor that does not promote widespread changes in allele or genotype frequencies?

The Greater prairie chicken population in Illinois is a living example of which of these ?

A population that is infinitely large and in which mating is completely random is mostly likely to:

Question at position 21 What is the most important determinant of genetic differences between populations of humans across the world?RaceEthnicityGeographic distanceLocal adaptationClear my selection

Question at position 14 Genetic diversity amongst human populations is best explained by __________.cultural differencespopulation sizeethnicityracial categorizesgeographic distanceClear my selection

更多留学生实用工具

智能学习助手

风格化写作助手

论文查重助手

文献引用助手

课堂转译助手

课堂笔记助手

Quiz搜索助手

学校历年真题

智能刷题助手

智能匹配练习

希望你的学习变得更简单