Gene Expression Programming (GEP) is a new evolutionary algorithm that evolves computer programs. The individuals of gene expression programming are encoded in linear chromosomes which are expressed or translated into expression trees (branched entities). Thus, in GEP, the genotype (the linear chromosomes) and the phenotype (the expression trees) are different entities (both structurally and functionally) that, nevertheless, work together forming an indivisible whole.
As in nature, the linear chromosomes consist of the genetic material that is passed on with modification to the next generation. Therefore, in GEP, all the genetic modifications take place in the chromosomes, and only the chromosomes are transmitted in the process of reproduction. After reproduction the new chromosomes are expressed forming the body or expression trees (ETs).
The ETs are themselves computer programs evolved to solve a particular problem and are selected according to their capabilities in solving the problem at hand. With time, populations of such computer programs discover new traits and become better adapted to a particular selection environment (for instance, a set of experimental results) and, hopefully, a good solution evolves.
Due to the genotype/phenotype representation and to the multigenic organization of GEP chromosomes, this new algorithm surpasses the old GP system in 100-10,000 times.
To know all the details of this new algorithm, see the seminal GEP paper (http://www.gene-expression-programming.com/webpapers/gep.pdf) (published in Complex Systems) where the algorithm is fully described and applied to a vast set of problems, including symbolic regression, Boolean concept learning, and cellular automata.
In common speech, "gene" is often used to refer to the hereditary cause of a trait, disease or condition—as in "the gene for obesity." Speaking more precisely, a biologist might refer to an allele or a mutation that has been implicated in or is associated with obesity.
In molecular biology, a gene is considered to be the region of DNA (or RNA, in the case of some viruses) that determines the structure of a protein (the coding sequence), together with the region of DNA that controls when and where the protein will be produced (the regulatory sequence).
The existence of genes was first suggested by Gregor Mendel, who, in the 1860s, studied inheritance in pea plants and hypothesized a factor that conveys traits from parent to offspring.
In this practice, identifiable aspects of the phenotype, assumed as determined directly by genes in a consciously fl-boxed manner, were used as indicators or ‘windows’ for an outlook on the formal structure of the genotype.
Conceiving of the gene as a unit of transmission, recombination, mutation, and function, classical geneticists combined various aspects of hereditary phenomena whose interrelations were, as a rule, not simple one-to-one relationships.
Gene products are of course involved in these networks and their complex functions, but these functions are by no means defined by the genes alone.
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