Question

Four genes (A, B, C, and D) are on the same chromosome. The recombination frequencies are as follows: A-B: 19%; B-C: 14%; A-C: 5%; B-D: 2%; A-D: 21%; C-D: 16%. Based on this information, which sequence of genes is correct?

Answer 1

Answer:

A-C-B-D or D-B-C-A

Step-by-step explanation:

Basically, we need to arrange the genes(A,B,C and D) in such a manner that recombination frequencies of genes add up to form a proper sum of the frequencies that justifies the sequence.

Now, arranging all the recombination frequencies from highest to lowest:

A-D : 21%

A-B : 19 %

C-D : 16 %

B-C : 14 %

A-C : 5 %

B-D : 2%

We can start by mapping out the genes combination frequencies from largest to smallest and their sum should add up.

As you can see from the figure that the sequence properly sums it up hence giving us the answer.

A - C - B - D

or

D-B-C-A

Any other combination would not add the frequencies properly.

As shown:

A-D= 21%= (A-B) + (B-D) = (A-C) +(C-B) + (B-D)

A-B= 19% = (A-C)+(C-B)

C-D= 16% =(C-B) + (B-D)