What is the implication of the neutral theory for molecular evolution?

What is the implication of the neutral theory for molecular evolution?

• A. Most molecular evolution is driven by positive selection.
• B. Many mutations are selectively neutral; evolution at the molecular level is largely due to genetic drift.
• C. Genetic drift never affects allele frequencies.
• D. All variation is eliminated by selection.

Answer: (B)

Neutral mutations and genetic drift dominate molecular evolution. The neutral theory proposes that many new mutations do not affect fitness, so natural selection has little influence on their fate. Instead, random sampling of alleles in finite populations causes changes in allele frequencies over time—that’s genetic drift. Because most new mutations are neutral, the rate at which they become fixed roughly matches their rate of appearance, creating a molecular clock. This explains why many DNA changes accumulate without changing protein function and why selection isn’t always the main driver of sequence evolution. So the best statement reflects that many mutations are selectively neutral and evolution at the molecular level is largely due to genetic drift. The other ideas contradict this view: the notion that most molecular change comes from positive selection overstates adaptive changes; drift never affects allele frequencies is false; and the idea that all variation is eliminated by selection ignores ongoing neutral variation and drift.

Neutral mutations and genetic drift dominate molecular evolution. The neutral theory proposes that many new mutations do not affect fitness, so natural selection has little influence on their fate. Instead, random sampling of alleles in finite populations causes changes in allele frequencies over time—that’s genetic drift. Because most new mutations are neutral, the rate at which they become fixed roughly matches their rate of appearance, creating a molecular clock. This explains why many DNA changes accumulate without changing protein function and why selection isn’t always the main driver of sequence evolution.

So the best statement reflects that many mutations are selectively neutral and evolution at the molecular level is largely due to genetic drift. The other ideas contradict this view: the notion that most molecular change comes from positive selection overstates adaptive changes; drift never affects allele frequencies is false; and the idea that all variation is eliminated by selection ignores ongoing neutral variation and drift.