Problem I A series of twopoint crosses were carried out amon

Problem I A series of two-point crosses were carried out among seven loci (a, b, c, d, e, f, and g), producing the following recombination frequencies. Map the seven loci, showing their linkage groups, the order of the loci in each linkage group, and distances between the loci of each linkage group. oci % Recombination Loci% Recombination a -b a c a -d 50 50 12 50 50 50 26 50 50 50 50 c -d C-f a f a -g 10 50 18 50 50 d- e d -f d -g e f e -g f -g b-e b -f b -g 50 50 50

Solution

50% recombination indicates that the genes assort independently. Less than 50% recombination indicates linkage.

        Starting with the most tightly linked genes b and d, we look for other genes linked to these and find only gene d has less than 50% recombination with a and g. So one linkage group consists of a, g, and d.

Starting with the most tightly linked genes b and d, we look for other genes linked to these and find only gene d has less than 50% recombination with a and b.

           So one linkage group consists of a, b, and d.

B and d------------------4

A and d----------------14

A and b---------------------10

-a-------------------10----------------b---------------------4---------------------------d

a--------------------------------------------14-------------------------------------------d

c and e------------------8

c and g----------------12

e and g---------------------18

e-------------------10----------------c---------------------8---------------------------g

e--------------------------------------------18-------------------------------------------g

Gene f is unlinked to either of these groups, on a third linkage group.