ABSTRACT
The mutation or targeting of a speci„c gene is one of the most attractive approaches in which scientists can gain insight into the potential function(s) of the gene of interest.1-5 To genetically alter the expression of a speci„c gene and explore the potential roles of the gene, strategies for stable overexpression or underexpression of a speci„c gene are widely employed.4-7 Nonetheless, up-or down-regulation of the expression of the gene of interest can only reveal the partial function of the gene. To prove the roles of an endogenous gene well, one may need to utilize another powerful tool-gene knockout or gene targeting by homologous recombination technology. This genetic approach can provide the highest level of control over producing mutations in an endogenous gene. Hence, it becomes an invaluable technique for investigators to make null mutations of transgenic mice to demonstrate in vivo gene function.9-11 This will allow one to address questions as to what a gene does in an organism, what it does for the body, and when and where in development a gene is mandated, using an animal model.
