In two-point recombination the chromosomes are paired and two points are randomly chosen as crossover points. The material between the recombination points is afterwards exchanged between the two parent chromosomes, forming two new daughter chromosomes.

Consider the following parent chromosomes:

Suppose bond 5 in gene 1 (between positions 4 and 5) and bond 7 in gene 2 (between positions 6 and 7) were chosen as the crossover points. Then, the following chromosomes are created:

It’s worth noticing that the non-coding regions of GEP chromosomes are ideal regions where chromosomes can be split to cross over without interfering with the ORFs and, in fact, during search, these regions are most favored by crossover.

One-point or two-point recombination are, after mutation, the operators most used in GEP. Indeed, the interplay between mutation and one-point and two-point recombination is an excellent source of genetic diversity and is more than sufficient to evolve solutions to virtually all problems.