Figure 1.

Quasispecies theory is described by using two fundamental equations. (A) The first equation describes the change in the concentration of mutant i with respect to time, xi(t); similarly, xk(t) describes the concentration of mutant k. The second equation expresses the error threshold relationship. The second equation has importance in virology and lethal mutagenesis, where the mutation rate pushes the virus beyond the error threshold and has benefits in drug development. (B) Error Threshold: the higher the mutations, the lower the infectivity.