Which of the following identifies the ultimate source of genetic variation in a population?

• A. Mutations
• B. Natural selection
• C. Genetic drift
• D. Gene flow

Answer: (A)

Mutations introduce new genetic material by altering DNA sequences, creating new alleles that weren’t present before. This is the raw material evolution relies on, giving populations fresh variation to act upon. Natural selection uses existing variation to shape which traits persist, but it doesn’t create new alleles. Genetic drift changes how common those alleles are over time by random chance, not by generating new ones. Gene flow can bring in alleles from other populations, increasing diversity within a population, but those alleles originally arose through mutation somewhere in the species’ history. So, mutations are the source of new genetic variation.