Two pure line of tomato were crossed. Line 1 had red fruit (R) and yellow flower
ID: 99202 • Letter: T
Question
Two pure line of tomato were crossed. Line 1 had red fruit (R) and yellow flowers (Wf), line 2 had yellow (r) fruit and white (wf) flowers. The F1 had red fruit and yellow flowers (Rr/Wfwf). The F1 was selfed to produce the following F2: 271 R Wf, 26 R wf, 30 r Wf and 73 r wf. Test for linkage and estimate the recombination frequency. Consider an SNP with the recombination frequency 0.12 to the “R” locus, away from “Wf”. What is the recombination frequency between the SNP and Wf given (the not so realistic) assumption that Haldane’s mapping function is valid in this region? What is the coefficient of coincidence?
Explanation / Answer
Recombination frequency = (recombinants)/(total offsprings) x 100
= (26+30)/(271+26+30+73) x 100
= 56/400 x 100
= 14% (0.14)
When the distance is small between linked genes, according to Haldane's mapping function, the recombinant frequency is equal to distance between genes.
Therefore, the recombination frequency between SNP and Wf is 0.12
Coefficient of coincidence = actual recombinant frequency/ expected recombinant frequency
= 0.12/0.14
= 0.857
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