Question
Three gene loci A, B and C are all located on chromosome Z in corn. The map below indicates the map distances of these loci. The interference between these genes in 0.4. The recessive mutant alleles of these loci and designated a, b, and c. A pure-breeding triple recessive corn plant (a, b, c) was crossed with a corn plant homozygous for the wild-type traits. The resulting F1 plant was testcrossed with a triple homozygous recessive plant and 1000 progeny were counted. List the expected phenotypic classes of progeny, the cross-over class each represents, and the expected # of progeny in that class.
Explanation / Answer
Different Phenotype classes are
Parental: ABC & abc = 453 & 410
Double cross overs: AbC & aBc = 5 & 8
Single cross over between A&B: Abc & aBC = 50 & 57
Single cross overs between B & C: ABc & abC = 9 & 8