Two genes in chromosome 7 of corn are identified by the recessive alleles gl (glossy), determining glossy leaves, and ra (ramosa), determining branching of ears. When a plant heterozygous for each of these alleles was crossed with a homozygous recessive plant, the progeny consisted of the following genotypes with the numbers of each indicated:

a) Do the chromosomes of the doubly heterozygous parent demonstrate coupling or repulsion with respect to genes gl and ra?

b) Using the notation for crosses with linked genes, draw the genotype of the doubly heterozygous parent.

c) Estimate the frequency of recombination between these genes.