In corn the leaf shine gene has two alleles g glossy determi

In corn, the leaf shine gene has two alleles g (glossy) determining glossy leaves, and G (dull); The ear branching gene has two alleles; the b allele (branched), determining branching of ears and the B allele (normal allele). When a plant heterozygous for each of these alleles was testcrossed, the progeny consisted of the following phenotypes with the numbers of each indicated.

dull, normal                23

dull, branched             188     

glossy, normal            172

glossy, branched         17   

a. What is the distance between the leaf shine gene and the ear branching gene?

b. In what arrangement (cis or trans) are the alleles in the heterozygous parent?

Solution

A).

Test cross--- GgBb (dull, normal) X ggbb (glossy, brandched)

Parental combinations= dull, branched and glossy, normal

Recombinants = dull, normal & glossy, branched

% of recombination frequency = distance between the genes(map units)

Recombinants = 40

Total = 400

Recombination frequency -= 40/400 * 100= 10%

Distance between the genes= 10 map units

B).

Dominant allele of one gene and recessive allele of the other gene present on the same chromosome, hence it is called as Trans arrangements.

The configuration of heterozygous parent= Dg/dG