The parameters of the GA are the same as GAs 1-3, except slightly different crossover and mutation steps. For crossover, the sequence of one parent is randomly selected, and the monomers can come from either parent or both. During mutation, either the sequence or a monomer will be replaced. When evaluating fitness, each donor was paired with the top 200 NFAs from GAs 1-3, and the highest PCE is set as that donor's score.