Gene flow is best described as which of the following?

• A. The transfer of alleles between populations
• B. Random fluctuations in allele frequencies by chance
• C. Migration preventing gene exchange
• D. The formation of new alleles within a population

Answer: (D)

Gene flow involves the movement of alleles between populations through migration and interbreeding, so alleles from one population enter another and change allele frequencies in both groups. This is the description of the transfer of alleles between populations. It differs from mutation, which creates new alleles within a population, and from genetic drift, which is random fluctuation of allele frequencies in small populations. It also undermines the idea that migration blocks gene exchange; migration is what enables gene flow by carrying alleles across populations.