Which process refers to random fluctuations in allele frequencies that can lead to loss of genetic variation, especially in small populations?

Which process refers to random fluctuations in allele frequencies that can lead to loss of genetic variation, especially in small populations?

• A. Genetic Drift
• B. Gene Flow
• C. Mutation
• D. Natural Selection

Answer: (A)

Random fluctuation in allele frequencies from one generation to the next, driven by chance rather than selection, is genetic drift. In small populations, these random shifts can have big effects: some alleles may become more common or disappear just by chance, and over time this can lead to fixation of certain alleles and loss of genetic variation overall. Because drift is not guided by fitness, it can operate independently of which traits are advantageous. Other forces behave differently. Gene flow involves movement of alleles between populations and tends to increase variation within the population and reduce differences between populations. Mutation introduces new alleles into the gene pool, increasing potential variation, though it acts as a source of new variation rather than a random change in existing allele frequencies. Natural selection changes allele frequencies based on differential survival and reproduction, so it is driven by fitness rather than random sampling.

Random fluctuation in allele frequencies from one generation to the next, driven by chance rather than selection, is genetic drift. In small populations, these random shifts can have big effects: some alleles may become more common or disappear just by chance, and over time this can lead to fixation of certain alleles and loss of genetic variation overall. Because drift is not guided by fitness, it can operate independently of which traits are advantageous.

Other forces behave differently. Gene flow involves movement of alleles between populations and tends to increase variation within the population and reduce differences between populations. Mutation introduces new alleles into the gene pool, increasing potential variation, though it acts as a source of new variation rather than a random change in existing allele frequencies. Natural selection changes allele frequencies based on differential survival and reproduction, so it is driven by fitness rather than random sampling.