In gene recombination an entire gene is exchanged during crossover. The exchanged genes are randomly chosen and occupy the same position in the parent chromosomes. Consider the following parent chromosomes:

012345678012345678012345678
/aa-abaaa/a*bbaaab/Q*+aaaab
/-*/abbabQ+aQbabaa-Q/Qbaaba

Suppose gene 2 was chosen to be exchanged. In this case the following offspring is formed:

012345678012345678012345678
/aa-abaaaQ+aQbabaa/Q*+aaaab
/-*/abbab/a*bbaaab-Q/Qbaaba

The newly created individuals contain genes from both parents. Note that with this kind of recombination, similar genes can be exchanged but, most of the time, the exchanged genes are very different and new material is introduced into the population.

It is worth noting that this operator is unable to create new genes: the individuals created are different arrangements of existing genes. In fact, when gene recombination is used as the unique source of genetic variation, more complex problems can only be solved using very large initial populations in order to provide for the necessary diversity of genes (see section 6.1). However, the creative power of GEP is based not only in the shuffling of genes or building blocks, but also in the constant creation of new genetic material.