Any sequence in the genome might become an IS element and, therefore, these elements are randomly selected throughout the chromosome. A copy of the transposon is made and inserted at any position in the head of a gene, except the first position. The transposition operator randomly chooses the chromosome, the start and termination points of the IS element, and the target site. It is worth pointing out that the implementation of this operator as described here, slightly differs from the original implementation (Ferreira 2001) where the length of the IS elements was a priori chosen.

Consider the following chromosome composed of three genes, each with a head size of six:

Suppose that the sequence “a/-” in gene 3 (positions 3-5) was picked up as an IS element to be then inserted between positions 1-2 in gene 2, obtaining:

Note that, in this case, a perfect copy of the transposon appears at the site of insertion. Note also that a sequence with as many symbols as the IS element is deleted at the end of the head (in this case, the sequence “a*a” was deleted). Thus, despite this insertion, the structural organization of chromosomes is maintained and, therefore, all the new individuals created by IS transposition are syntactically correct programs.