Solutions For An Introduction to Genetic Analysis Chapter 6 Problem 56P

The pedigree concerns with the eye phenotypes in Tribolium beetles. It represents black eyes, brown eyes, which crosses with the eyeless phenotype.

a) The black and eyeless cross produces black and brown progeny on the first instance while in the second instance produces black and eyeless progeny. On further analysis, cross between two black produces brown progeny and a cross between the brown and eyeless produces brown progeny. A cross between brown and black cross produces eyeless beetles. But the question here is that whether there are two genes or one gene with three alleles.

To identify, we need to proceed through trial and error method. There are two possibilities comprising either with one gene or two genes.

One gene – Let us assume that gene is E along with the following designations:

E ¹ = black

E ² = brown

E ³ = eyeless

Based on the various crosses black > brown > eyeless genotypes in the pedigree develop: