Question

Mexican cave-dwelling fish have evolved reduced eye size and other morphological traits associated with living in total darkness. Researchers produced an inbred (or true-breeding) line of Mexican cave-dwelling fish and an inbred line from a closely related surface-dwelling fish with which the cave-dwelling fish readily hybridize. The researchers then crossed the two inbred lines to produce F1 and F2 offspring that were raised in the same laboratory. The researchers estimated the phenotypic variation in eye diameter for the F1 (hybrid) offspring at 2.0 and the phenotypic variation in F2 offspring at 8.0.

(a)What is the genotypic variation of the F1 offspring? Why?

(b)What is the best estimate for environmental variation in the F2 offspring?

(c)What is the broad-sense heritability of eye size in the F2 generation?

Answer 1