Gene targeting allows one to create null mutations in mice and to analyze h
ow the mutant organism responds to the lack of a single gene product. This
has facilitated the molecular dissection of such complex characteristics as
mammalian brain function and behavior. including learning. memory. aggress
ion, and maternal behavior to mention a few. However, the interpretation of
the phenotypical changes that arise in null mutant mice has been questione
d. The possibility that genes other than the targeted one may contribute to
phenotypical alterations has been raised and the importance of compensator
y mechanisms has been brought to attention. This review focuses on recent a
dvances in the literature that illustrate the caveats associated with gene
targeting and also presents an overview of potential solutions for the disc
ussed problems. (C) 2001 Elsevier Science BN. All rights reserved.