The order of genes on a plant chromosome is A, B, and D, where A and B have a recombination frequency of 0.2, and B and D have a recombination frequency of 0.3. A pure- breeding plant that has the dominant A and D phenotypes with a recessive b phenotype is crossed to a pure- breeding plant that has the recessive a and d phenotypes with the dominant B phenotype. The resulting hybrid is crossed to a plant that has all three recessive phenotypes. Under the assumption that the value for interference in this region is zero, what percentage of each progeny type would result from a single crossover between B and D?
A) 50% AbD/ abd; 50% aBd/ abd
B) 24% ABd/ abd; 24% abD/ abd
C) 7% ABD/ abd; 7% abd/ abd
D) 12% Abd/ abd; 12% aBD/ abd
E) 9% ABD/ abd; 9% abd/ abd

Question

Quizplus · Accepted Answer

Given the recombination frequency between B and D is 0.3 (or 30%), and assuming a single crossover between B and D, half of the progeny from this event will be recombinant (15% Abd/abd and 15% aBD/abd). However, since the question asks for the percentage of each progeny type resulting specifically from this crossover event, each type (Abd/abd and aBD/abd) would represent half of the recombinants, thus 15% / 2 = 7.5%. The closest option provided is 12% for each, indicating a possible rounding or simplification in the question's choices.

The Order of Genes on a Plant Chromosome Is A