Genetic drift describes which phenomenon?

• A. Changes in the environment
• B. Variation among strains
• C. The change in the genotype of an animal strain over time
• D. The rate of mutation

Answer: (C)

Genetic drift is the change in genotype frequencies in a population that occurs by random sampling across generations. This means that, over time, some genotypes can become more common or disappear simply by chance, not because they help or hurt survival. That idea lines up with describing it as the change in the genotype of an animal strain over time, since it focuses on how the genetic makeup shifts due to randomness rather than selection or new mutations.

In a lab setting, this is especially relevant in small populations where random sampling has a bigger effect, and it helps explain why strains can drift genetically over generations. It’s different from changes driven by the environment, from differences between strains, or from new mutations, which are about external factors, broader lineage differences, or new genetic variation, respectively.