Platyfish with spots have an X-linked gene that produces the spots.All platyfish have an autosomal repressor that inhibits the expression of the spot-producing gene.The closely related swordtail lacks both the spot-producing gene and the repressor.In backcrosses between these two species, some hybrids receive the spot-producing gene, but not the repressor.These individuals can develop malignant tumors, because the expression of the spot-producing gene is not properly regulated.This appears to be an example of
A) speciation via reinforcement.
B) polymorphism.
C) the Dobzhansky-Muller model of speciation.
D) hybrids surviving just as well as nonhybrids.
E) an inability to hybridize.

Question

Quizplus · Accepted Answer

The situation described in the question fits with the Dobzhansky-Muller model of speciation, which suggests that the hybridization of closely related species can result in the expression of incompatible genes and ultimately lead to reproductive isolation. In this case, the hybrids that receive the spot-producing gene but lack the repressor are not able to properly regulate its expression, leading to the development of tumors. This represents a case of genetic incompatibility between the two species.

Platyfish with Spots Have an X-Linked Gene That Produces the Spots.All