Question

If locus B is 8 cM from locus D and Locus D is 12 cm from locus C, what is the distance (in cM) from locus B to C - Explain your reasoning.

Answer 1

There are 3 locus given the order of them can be written in two forms BDC or DBC

If BDC is the gene order, distance between Band D =8cM, distance between D and C=12cM the distance between Locus B to C=8+12=20cM

If DBC is the gene order distance between D and B =8cM distance between D and C=12cM, Distance between B and C= 12-8=4cM

Map distance are roughly additive hence there can be 2 possibities for B to C distance= 20 cM or 4 cM

BDC B----------------8cM---------------D--------------------------------------12cM-----------------------------------C

DBC D------------------8cM------------B--------4cM------------C