What is a cause of the absence of the A and B alleles in Native American populations?

Question

Quizplus · Accepted Answer

The absence of the A and B alleles in Native American populations is due to the founder effect. When a small group breaks away from a larger population to start a new population, the genetic variation of the smaller group is limited to that of the founders. In this case, the founders of Native American populations did not have the A and B alleles, so subsequent generations of Native Americans also did not have these alleles as the population grew and expanded.

What Is a Cause of the Absence of the a and B