All RIS elements start with a function, and thus are chosen among the sequences of the heads. For that, a point is randomly chosen in the head and the gene is scanned downstream until a function is found. This function becomes the start position of the RIS element. If no functions are found, the operator does nothing.

Typically, I use a root transposition rate (p_ris) of 0.1 and a set of three RIS elements of different sizes. This operator randomly chooses the chromosome, the gene to be modified, the start of the RIS element, and its length. Consider the two-genic chromosome below:

Suppose that the sequence ‘Q/+’ in gene 1 was randomly chosen to become an RIS element. Then, a copy of the transposon is made into the root of the gene, obtaining:

Note that during transposition, the whole head shifts to accommodate the RIS element, losing, at the same time, the last symbols of the head (as many as the transposon length). In this case, the sequence ‘++/’ was deleted, and the transposon became only partially duplicated. As with IS elements, the tail of the gene subjected to transposition and all nearby genes stay unchanged. Note, again, that the newly created programs are syntactically correct because the structural organization of the chromosome is maintained.