What is the definition of genetic drift?

• A. Systematic change in allele frequencies due to natural selection
• B. Random fluctuation in allele frequencies in a population
• C. Intentional change in gene expression
• D. Random mutation that always leads to positive adaptations

Answer: (B)

The definition of genetic drift is centered around the concept of random fluctuations in allele frequencies within a population. This phenomenon occurs typically in small populations, where chance events can significantly affect which alleles are passed on to subsequent generations. Unlike natural selection, which is a systematic change based on advantageous traits that improve fitness, genetic drift does not favor any allele based on its utility; rather, it results from random sampling effects that can lead to changes in allele frequencies purely by chance.

For example, if a natural disaster randomly affects individuals in a population, certain alleles might be lost simply because those individuals did not survive, regardless of the characteristics they possessed. Over time, these random changes can lead to a decrease in genetic diversity within the population as certain alleles may become more or less common by chance alone.

This understanding of genetic drift highlights its role as a mechanism of evolution alongside natural selection and mutation. It is particularly important in population genetics as it showcases how populations can evolve in ways that are not directly related to the adaptive value of traits, emphasizing the role of chance in the evolution of species.