Question

You sample a number of cells that have undergone meiosis looking for the production of recombinants between the genes ec, vg, and s. You find 10 cells with no crossovers between ec and s. 30 with 1 crossover between ec ands, 10 with 2 crossovers between ec and s, and zero with three or more crossovers. What is the map distance between the genes ec and s? 1.2 CM 0.8 CM 0.6 CM 0.2 CM 1.0 CM

Answer 1

1. No cross over Parental = 10
Single cross over ec and s (SCO) = 30
Double cross over (DCO) = 10

Recombinant frequency = SCO + DCO / Total
                      = 30 + 10 / 50
                      = 0.8 cM

2. Coefficient of coincidence is near one

Coefficient of coincidence COC = Observed DCO / Expected DCO

Observed DCO = 15/500 = 0.03
Expected DCO = 0.15 X 0.25 = 0.0375

      COC = 0.03 / 0.0375 = 0.8
The COC is near to 1

Interference = 1 - COC
             = 1 - 0.8 = 0.2
Interference is low.