Final answer:
The unique mutation causing PKU in Yemenite Jews is likely due to a founder effect, a phenomenon where a new population has a different allele frequency than the original larger population because it was founded by a small, non-representative group of people.Hence, the correct answer is option A.
Step-by-step explanation:
The unique mutation found only in Yemenite Jews that causes phenylketonuria (PKU) is most likely the result of a founder effect. The founder effect is a phenomenon that occurs when a new population is established by a very small number of individuals from a larger population, carrying with them only a subset of the genetic variation present in the original population. This can lead to certain genetic traits being overrepresented in the new population. Examples of the founder effect include the Amish population, which has a higher incidence of Ellis-van Creveld syndrome, and the Afrikaner population in South Africa, which shows high incidences of Huntington's disease and Fanconi anemia due to the genetic makeup of the original Dutch settlers.