Map Distance:


To figure out the distances, we must identify our single crossover classes. We've got four of them: BAC, bAc, BaC and bac. Note that this is two pairs of reciprocals (BACand bac are reciprocals and bAc and BaC are also reciprocals). Again, we want to compare these to the parentals which are most like them to determine just where the crossover occurred to produce them. Comparing single crossover BAC to parental bAC, we see that it has recombined between the B and the A loci. Same for its reciprocal. Comparing the BaC single crossover to the Bac parental, we see that it has recombined between the A and the C genes, as has its reciprocal. Note also that the numbers of offspring give you hints as to which crossover classes go together.Now we are ready to calculate distances. We have four offspring classes which have recombined between the B and the A genes. These are the single crossovers BAC (95) andbac (95) as well as the double crossovers Bac (5) and bAC (5). This gives us a total of 200 offspring who have crossed over between these two genes. There are a total of 1700 offspring, so we'd calculate this distance as (200/1700) x 100, which equals 11.8. So we've calculated a distance of 11.8 LMU between genes B and A.There are also four offspring classes which have recombined between the A and C genes. bAc (50), BaC (50) and again, our double crossover classes BAc (5) and baC (5), for a total of 110.

Calculating: (110/1700) x 100 = 6.5 LMU between genes A and C.To calculate the distance between B and C, just add 11.8 and 6.5, to get 18.3 LMU.