Answer

(A) Bottleneck Effect (Genetic Drift)

Explanation

This question is about understanding how genetic diversity and certain genetic conditions become prevalent in specific populations due to historical events and population dynamics. The critical aspect here is identifying the correct pattern of genetic change described in the scenario provided.The scenario mentions that after World War II and the Holocaust, more severe illnesses exist among certain Jewish groups, notably the Ashkenazi Jews, who have a high chance of suffering from Tay-Sachs disease. This situation hints at a genetic pattern influenced by a significant reduction in population size and subsequent population recovery, which affects the genetic diversity and prevalence of specific genetic conditions within the population.Option (A), the Bottleneck Effect, refers to a process where a significant portion of a population is destroyed or prevented from reproducing, leading to a reduction in genetic diversity. The survivors' genes become more common in the population, potentially increasing the frequency of genetic diseases if those survivors carry such genes. This effect seems to align with the scenario described, where a drastic reduction in population size (due to the Holocaust) could lead to an increase in the prevalence of certain genetic conditions like Tay-Sachs disease among survivors and their descendants.Option (B), the Founder Effect, occurs when a new colony is started by a few members of the original population. This small population size means that the new colony may have reduced genetic variation from the original population and a different prevalence of certain genetic traits. While this effect can also lead to an increase in specific genetic conditions, the scenario described does not specifically mention the formation of a new colony or population from a small group of individuals; instead, it focuses on the impact of a population reduction due to historical events.Option (C), Natural Selection, involves the differential survival and reproduction of individuals due to differences in phenotype. It is more about traits that offer a reproductive advantage in a specific environment, rather than the genetic prevalence of diseases due to population size reduction or founder effects.Given the scenario's emphasis on the historical reduction in population size and the subsequent increase in the prevalence of a genetic condition (Tay-Sachs disease), the most accurate pattern of genetic change described is: