Genetic drift is influenced most by population size; which scenario increases its impact?

• A. Large populations
• B. Small populations
• C. Random mutation
• D. Gene flow

Answer: (B)

Genetic drift is the random fluctuation of allele frequencies from generation to generation due to sampling effects. The smaller the population, the less representative the sample of alleles is of the overall gene pool, so chance events have a much larger impact. In a tiny population, an unlucky draw can quickly fix or lose an allele, dramatically changing genetic makeup and reducing variation by chance. Large populations buffer against drift because sampling error is diluted across many individuals, making frequencies more stable. Random mutation introduces new alleles but isn’t what increases drift’s impact, and gene flow tends to smooth differences between populations, reducing drift’s effects. So, a small population increases the influence of genetic drift.