In corn, the genes ‘v’, ‘pr’, and ‘bm’ are all on chromosome 5, but not necessar

Question

In corn, the genes ‘v’, ‘pr’, and ‘bm’ are all on chromosome 5, but not necessarily in the order given. A testcross between a plant that is a carrier for all three genes is performed and the following progeny are observed. Which genes are closest together?

+ pr bm 20
v + + 20
+ pr + 19
v + bm           21
+ + bm          703
v pr + 694
+ + +             725
v pr bm           676

Select one:

a. all genes are the same distance from each other

b. it is impossible to tell

c. ‘v’ and ‘bm’

d. ‘pr’ and ‘bm’

e. ‘v’ and ‘pr’

Explanation / Answer

Calculations of distances

DCO between v & bm = 676+ 725 = 1401

SCO between v & bm = 21 + 19 = 40

Total crossing over between v & bm = 1441

1441/2878* 100 = 50.06 Map Units  

DCO between bm & pr = 676+ 725 = 1401

SCO between bm & pr = 20 + 20 = 40

Total crossing over between bm & pr = 1441

1441/2878* 100 = 50.06 Map Units  

V 50.06mu pr 50.06 mu bm

Therefore, A option is correct.

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