Question

The disproportionately high appearance of polydactylism among the Amish suggests that _______.
a.
it is a common mutation
b.
it is a common birth defect in Pennsylvania
c.
it was overrepresented in the gene pool of the original Amish settlers
d.
humans are prone to this birth defect

Answer 1

First, the question tells you polydactylism is "disproportionately" frequent among the Amish. You can rule out a and d because those describe the whole of humanity. The Amish do not make up that large of a portion of the Pennsylvanian population so b isn't all that relevant. The Amish are a common example for illustrating the founder effect in evolutionary biology and population genetics; if the founders of a small population have a genetic quirk (even in one individual), that quirk will be more common in that population than in other, larger populations.

Answer 2

The answer would be c.