What best describes genetic drift?

• A. A change in the breeding efficiency of a genetically engineered group of animals
• B. The differences among strains of genetically engineered animals
• C. The differences in genotype between wild type and genetically engineered animals
• D. The change in the genotype of an animal strain over time

Answer: (D)

Genetic drift is the random fluctuation of allele frequencies from one generation to the next within a population, caused by chance events rather than by natural selection. Because these changes are random, they can alter the genotype makeup of an animal strain over time, especially when the population is small. Over generations, some alleles may become more common or disappear entirely by luck, and this can even lead to fixation of certain alleles.

This concept is different from changes driven by breeding efficiency, as it isn’t about how well a trait is bred or selected for. It’s also not about comparing different strains created through engineering or about differences between wild-type and engineered animals, which reflect design or deliberate modification rather than random shifts in allele frequencies.