You generated a plant that is heterozygous for three quantit

You generated a plant that is heterozygous for three quantitative trait loci (QTL). In the heterozygous state, each locus has one allele that contributes one dose of trait (pigment) and another allele that does not contribute a dose to the trait; genotype: R1/r1; R2/r2; R3/r3. If you testcross this plant (by r1/r1; r2/r2; r3/r3 all “0-dose” alleles) what distribution of pigment doses would be observed in the progeny?

The answer is

1/8, three dose; 3/8, two dose; 3/8, one dose; 1/8, zero dose

can someone walk through the process?

Solution

A cross between R1r1R2r2R3r3 x r1r1r2r2r3r3

R1r1R2r2R3 : 3 dose = 1/8

r1r1R2r2R3r3 + R1r1R2r2r3r3 + R1r1r2r2R3r3 : 2dose = 3/8

R1r1r2r2r3r3 + r1r1R2r2r3r3 + r1r1r2r2R3r3 : 1 dose = 3/8

r1r1r2r2r3r3: 0 dose = 1/8