Fruit color in a particular plant is controlled by a set of three QTLs (quantitative trait loci,or "polygenes")that work in an equal and additive manner.Each QTL has two alleles (i.e. ,A and a);each allele represented by a capital letter produces one dose of yellow pigment,while alleles represented with lower case letters do not produce any pigment at all.
-A trihybrid plant (A/a;B/b;C/c)is selfed.Assuming no effects of the environment,what proportion of the offspring will have the same fruit color phenotype as the dihybrid parent?

Question

Quizplus · Accepted Answer

The dihybrid parent has a genotype of A/a; B/b; C/c, which means it has three doses of the yellow pigment (one from each of the A, B, and C alleles). When selfed, the offspring can have 0 to 6 doses of the pigment, depending on the combination of alleles they inherit. To have the same fruit color phenotype as the parent, the offspring must also have three doses of the pigment. The possible genotypes that give three doses are A/a; B/b; c/c, A/a; b/b; C/c, a/a; B/b; C/c, A/A; B/b; c/c, A/A; b/b; C/c, and a/a; B/B; C/c. Calculating the probability for each of these genotypes and summing them gives a total probability of 0.312.

Fruit Color in a Particular Plant Is Controlled by a Set