Use the following information to answer the question.

The numbers in the boxes are the recombination frequencies in between the genes (in percent).
In a series of mapping experiments, the recombination frequencies for four different linked genes of Drosophila were determined as shown in the figure. Based on this information, what is the order of these genes on a chromosome map?
A) rb-cn-vg-b
B) cn-rb-b-vg
C) b-rb-cn-vg
D) vg-cn-b-rb

Question

Use the following information to answer the question.

The numbers in the boxes are the recombination frequencies in between the genes (in percent).
In a series of mapping experiments, the recombination frequencies for four different linked genes of Drosophila were determined as shown in the figure. Based on this information, what is the order of these genes on a chromosome map?
A) rb-cn-vg-b 
B) cn-rb-b-vg 
C) b-rb-cn-vg 
D) vg-cn-b-rb

Quizplus · Accepted Answer

The gene with the lowest recombination frequency should be in the middle. In this case, the gene with the lowest recombination frequency is cn (9%), so it should be in the middle. The recombination frequency between cn and rb is 22%, and the recombination frequency between rb and b is 8%, so the order can be cn-rb-b. The recombination frequency between b and vg is 21%, so the final order is b-rb-cn-vg.

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