Mixed infections of two rIIA mutants on E. coli B produce wild-type recombinants that can infect
the K12 strain (left).
The plate at right is a B strain control that reflect total phage progeny.
To calculate the frequency of recombination:
2 (recombinant phages) / total phages):
2 (4 * 103 / 8 * 109) = 2 (0.5 * 10-6) = 10-6
We need to multiply by 2 since only one of the two reciprocal recombinants is
detected.
