Question

13.5 Two loci P and Bz are normally 36 cM apart of the same arm of a certain plant chromosome. An inversion spans one fourth of this region but does not include either of the loci. What recombinant frequency between P and Bz would occur in plants that are heterozygous for the inversion? What recombinant frequency between P and Bz would occur in plants that are homozygous for the inversion?

Answer 1

Distance between P and Bz = 36 mu
They are located on the same chromosome.

Recombinant frequency between P and Bz in plants that are heterozygous for the inversion:
If the inversion is heterozygous, the products of the crossing over within the inversion are inviable.
Since a paracentric inversion spans about one-fourth of the region but does not include either of these loci, the recombination frequency will be reduced by 25%.
= 36 - (36 X 0.25) = 27%

Recombinant frequency between P and Bz in plants that are homozygous for the inversion:
If the inversion is homozygous, the products of the crossing over within the inversion are viable.
So, the recombination frequency = 36%