When multiple copies of a polypeptide encoded by a gene self-assemble to form a complex, this protein structure is referred to as a "multimer".    Genes that encode multimer-forming polypeptides appear to be common.  When a multimer is formed from polypeptides produced by two different mutant alleles of a particular gene, the mixed multimer may exhibit greater functional activity than the unmixed multimers formed by each of the mutants alone.  In such a case, the phenomenon is referred to as intragenic complementation.   Jehle pointed out that, when immersed in a liquid and intermingled with other molecules, charge fluctuation forces favor the association of identical molecules as nearest neighbors.