Question

Three-point testcrosses are often used to map genes. The two least frequent classes from such crosses usually represent which of the following types of progeny?

Answer 1

In a three-point testcross, the two least frequent classes of progeny represent the recombinant genotypes resulting from recombination events between the linked genes. These genotypes differ from the parental genotypes.

Step-by-step explanation:

In a three-point testcross, the two least frequent classes of progeny represent the recombinant genotypes resulting from recombination events that occurred between the linked genes during meiosis. These recombinant genotypes are different from the parental genotypes, which are the two most frequent classes of progeny. Recombination events result in the formation of new allele combinations, known as nonparental types, that are different from the allele combinations present in the original parents. Linkage between genes is indicated when the two least frequent classes are observed more frequently than would be expected if the genes were unlinked and undergoing independent assortment.