[Campbell Biology P.354] Three genes b, cn, vg are on the same chromosome. The recombination... | Practice Question

Three genes b, cn, vg are on the same chromosome. The recombination frequencies are: b-cn = 9%, cn-vg = 9.5%, and b-vg = 17%. What is the most likely order of these genes on the chromosome?

  • A: b - cn - vg
  • B: cn - b - vg
  • C: b - vg - cn
  • D: The order cannot be determined from this data.

Explanation

To determine the gene order, find the largest recombination frequency 17% for b-vg . This means b and vg are the farthest apart and are at the ends. The third gene, cn, must be in the middle. The distances confirm this: the distance from b to vg 17% is approximately the sum of the distances from b to cn 9% and cn to vg 9.5% .