Which genetic phenomenon occurs when there is a drastic reduction in population size that can lead to a loss of genetic diversity?

Which genetic phenomenon occurs when there is a drastic reduction in population size that can lead to a loss of genetic diversity?

• A. Founder Effect
• B. Gene Flow
• C. Genetic Bottleneck
• D. Artificial Selection

Answer: (C)

When a population drops to a very small number of individuals, the genetic material left behind represents only a tiny slice of what was present before. With so few carriers passing on genes, random changes in allele frequencies—genetic drift—can quickly erase many alleles. This leads to lower genetic diversity and often higher relatedness among survivors, which can reduce the population’s ability to adapt to new challenges. This pattern, where a drastic reduction in population size causes a loss of variation, is called a genetic bottleneck. A related idea is the founder effect, where a new population founded by a small group also has limited diversity, but the scenario described emphasizes the population size crash itself. Gene flow would mix genes between populations and tends to increase diversity, while artificial selection involves human-directed breeding and doesn’t inherently describe a size-related bottleneck.

When a population drops to a very small number of individuals, the genetic material left behind represents only a tiny slice of what was present before. With so few carriers passing on genes, random changes in allele frequencies—genetic drift—can quickly erase many alleles. This leads to lower genetic diversity and often higher relatedness among survivors, which can reduce the population’s ability to adapt to new challenges. This pattern, where a drastic reduction in population size causes a loss of variation, is called a genetic bottleneck. A related idea is the founder effect, where a new population founded by a small group also has limited diversity, but the scenario described emphasizes the population size crash itself. Gene flow would mix genes between populations and tends to increase diversity, while artificial selection involves human-directed breeding and doesn’t inherently describe a size-related bottleneck.