Genetic drift is a key concept in evolutionary biology, describing how random fluctuations in allele frequencies can shape the genetic makeup of populations over generations. While often overshadowed by natural selection, genetic drift is especially powerful in small populations and can have lasting effects on genetic diversity. However, misconceptions about what genetic drift does or does not do are common. Let’s clarify which statements about genetic drift are true and which are not, focusing on the statement: “It generates variance in population.”

What Is Genetic Drift?

Genetic drift refers to the random change in allele frequencies within a population due to chance events, rather than selective pressures. This randomness can lead to the loss or fixation of alleles, particularly in small populations, and is a non-selective process that affects all alleles, regardless of their impact on fitness.

True Statements About Genetic Drift

Let’s examine the commonly cited statements about genetic drift:

The Incorrect Statement: “It generates variance in population”

The statement “It generates variance in population” is NOT true regarding genetic drift as an evolutionary force.

Why Is This Statement Incorrect?

• Genetic drift does not generate genetic variance; it reduces it.
  Genetic drift tends to decrease genetic variation within a population over time. As alleles are randomly lost or fixed, the gene pool becomes less diverse. This is especially problematic for small populations, where genetic drift can rapidly eliminate rare alleles, leaving the population with less genetic diversity to adapt to future environmental changes.

• Variance is lost, not created.
  Once an allele is lost due to drift, it cannot reappear unless reintroduced by mutation or gene flow. This loss of allelic diversity can make populations more vulnerable to extinction or disease.

Supporting Evidence

• “Genetic drift can lead to the loss of genetic variation, as alleles are randomly lost or fixed in a population.”

• “The 10:0 situation illustrates one of the most important effects of genetic drift: it reduces the amount of genetic variation in a population.”

• “Genetic drift may cause gene variants to disappear completely and thereby reduce genetic variation.”

Why Is This Distinction Important?

Understanding that genetic drift reduces rather than generates variance is crucial for:

• Conservation biology: Small, endangered populations are at risk of losing genetic diversity through drift, making them less adaptable and more prone to extinction.

• Evolutionary theory: While mutation and gene flow introduce new genetic variance, genetic drift acts as a random filter, often removing it from the population over time.

• Population management: Strategies to maintain genetic diversity must consider the impact of drift, especially in breeding programs or habitat restoration.

Conclusion

While genetic drift is significant in small populations, leads to fixation or loss of alleles, and causes changes in allele frequency, it does not generate variance in a population. Instead, genetic drift reduces genetic variation by randomly eliminating alleles, which can have lasting consequences for the adaptability and survival of populations. Recognizing this helps scientists and conservationists develop better strategies to preserve biodiversity and understand the true dynamics of evolutionary change.