Modification of Specific Chromosomal Loci in Mammalian Cells by Recombination.

Biochemistry and genetics epitomize what is called the reductionist approach to biology; single biological elements (for example, a protein, an enzyme, or a gene) are examined in great detail through a series of narrowly defined questions and experimental protocols. This approach can illuminate many phenotypic characteristics of complex systems, including whole organisms, if those phenotypes are the direct consequence of a single gene's function. [ABSTRACT FROM AUTHOR]