The addition of foreign genes or DNA fragments to a cell does not guarantee a change in the character (phenotypic expression) of an organism.

Expression of a gene is regulated along a very specific pathway, from transcription of the gene to mRNA, processing of the mRNA transcript prior to translation, and modification of the protein following translation for cellular transport and secretion.

Signaling and modifying proteins which regulate such pathways vary among species.

However, the process of gene cloning did allow scientists to answer questions about the structural organization of DNA, functioning of specific genes, regulation of gene activity, and DNA sequences responsible for such regulation.