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C. FERREIRA In Leandro N. de Castro and Fernando J. Von Zuben, eds., Recent Developments in Biologically Inspired Computing, pages 82-103, Idea Group Publishing, 2004.

Gene Expression Programming and the Evolution of Computer Programs

One-point Recombination
 

In one-point recombination the parent chromosomes are paired and split up at exactly the same point. The material downstream of the recombination point is afterwards exchanged between the two chromosomes.

Consider the following parent chromosomes, each composed of three genes:

012345678901201234567890120123456789012
*b-Qb/aaabaabQ**Q+*bbaaabb*Q--QQaabbbbb

-/bQa+aabbbba/Q*b/aababaaa-/a/a/abaaabb

Suppose bond 4 in gene 2 (between positions 3 and 4) was randomly chosen as the crossover point. Then, the paired chromosomes are both cut at this bond, and exchange between them the material downstream of the crossover point, forming the offspring below:

012345678901201234567890120123456789012
*b-Qb/aaabaabQ**Q/aababaaa-/a/a/abaaabb

-/bQa+aabbbba/Q*b+*bbaaabb*Q--QQaabbbbb

It is worth emphasizing that GEP chromosomes can cross over any point in the genome, continually disrupting old building blocks and continually forming new ones. Furthermore, due to both the multigenic nature of GEP chromosomes and the existence of non-coding regions in most genes, entire genes and intact open reading frames can be swapped between parent chromosomes. Thus, the disruptive tendencies of one-point recombination (splitting of building blocks) coexist side by side with its more conservative tendencies (swapping of genes and ORFs), making one-point recombination (and of course two-point recombination too) a very well balanced genetic operator. Furthermore, like all the other recombinational operators, when one-point recombination is used together with gene transposition, it is also capable of duplicating genes.

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