Any sequence in the genome might become an IS element, being therefore these elements 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. Typically, a transposition rate
(pis) of 0.1 and a set of three IS elements of different lengths is used. The transposition operator randomly chooses the chromosome, the start of the IS element, the target site, and the length of the
transposon.
Consider the following two-genic chromosome:
|
0123456789012345601234567890123456
-aba+Q-baabaabaabQ*+*+-/aababbaaaa |
Suppose that the sequence ‘a+Q’ in gene 1 (positions 3-5) was randomly chosen to become an IS element and transpose between positions 2-3 in gene 2, obtaining:
|
0123456789012345601234567890123456
-aba+Q-baabaabaabQ*+a+Q*+ababbaaaa |
Note that, on the one hand, the sequence of the transposon becomes duplicated but, on the other, a sequence with as many symbols as the IS element was deleted at the end of the head of the target gene (in this case the sequence ‘-/a’ was deleted. Thus, despite the insertion, the structural organization of chromosomes is maintained, and therefore all the new individuals created by transposition are syntactically correct programs.
|