Mutation and Repair Lab

Simplifications: each culture starts from 1,000 sensitive cells and doubles in step until it reaches the final size, so the number of cell divisions is about the final number of cells (N). Mutation events are drawn at random (Poisson) in each generation, a mutant's descendants are all resistant, every cell is plated, and there are no back mutations or growth differences. In the induced model, each cell instead has the same small chance of turning resistant when it meets the phage, set so the average count matches. The p₀ estimate is μ = −ln(p₀) ÷ N and needs some cultures with zero mutants.

Simplifications: counts are drawn at random around a smooth dose-response curve; real tests use replicate plates and positive controls. TA98 reverts by frameshifts and TA100 by base-pair substitutions. A result is called positive here when revertants reach at least twice the spontaneous level and rise with dose. Compound X and Compound Y are fictional; the other compounds behave in the way they are usually described.

Problems are randomly generated. Sequences are coding strands (same as mRNA, with T for U), read from the start codon. Rates can be typed as 3.2e-9, 3.2 x 10^-9 or 0.0000000032; answers within about 3% are accepted. The standard genetic code is drawn on the picture when you need it.