Gene targeting is a method for modifying the structure of a specific gene without removing it from its natural environment in the chromosome in a living cell. This process involves the construction of a piece of DNA, known as a gene targeting vector, which is then introduced into the cell where it replaces or modifies the normal chromosomal gene through the process of homologous recombination.

The Homologous Recombination Process

Homologous recombination is a process that occurs within the chromosome and which allows one piece of DNA to be exchanged for another piece. It is a cellular mechanism that is probably part of the normal process cells use to repair breaks in their chromosomes. Homologous recombination requires that the pieces of DNA undergoing recombination be almost identical (homologous) in sequence. In addition, sequences on either side of the target should be identical, to promote more efficient targeting...