This type of chromosome represents combination of ideas taken from Genetic Algorithms (GA), where chromosomes are linear structures of fixed length, and Genetic Programming (GP), where chromosomes are expression trees. The GEP chromosome is also a fixed length linear structure, but with some additional features which make it possible to generate valid expression tree from any GEP chromosome.

The theory of Gene Expression Programming is well described in the next paper: Ferreira, C., 2001. Gene Expression Programming: A New Adaptive Algorithm for Solving Problems. Complex Systems, Vol. 13, issue 2: 87-129. A copy of the paper may be obtained on the gene expression programming web site.