What is genetic drift?

What is genetic drift?

• A. Nonrandom mutation rate changes due to environment
• B. Random fluctuation of allele frequencies; stronger in small populations, can lead to fixation or loss of alleles independent of fitness
• C. Nonrandom survival of individuals due to fitness differences
• D. Gene flow between populations

Answer: (B)

Random changes in allele frequencies from one generation to the next, caused by chance sampling in finite populations. In small populations these random shifts have a bigger effect, and alleles can become fixed or lost purely by chance, regardless of whether they confer any advantage or disadvantage. Over time, this can reduce genetic variation within a population and lead to unpredictable evolutionary outcomes. This differs from natural selection, where allele frequencies change because certain variants confer higher fitness; it also isn’t about gene flow between populations or about mutation rate changes driven by the environment.

Random changes in allele frequencies from one generation to the next, caused by chance sampling in finite populations. In small populations these random shifts have a bigger effect, and alleles can become fixed or lost purely by chance, regardless of whether they confer any advantage or disadvantage. Over time, this can reduce genetic variation within a population and lead to unpredictable evolutionary outcomes. This differs from natural selection, where allele frequencies change because certain variants confer higher fitness; it also isn’t about gene flow between populations or about mutation rate changes driven by the environment.