RESULTS AND DISCUSSION
The introduction of foreign DNA into living cells, embryos,
or organisms is one of the most important analytical
tools for in vivo studies. It has permitted the production
of transgenic animals such as knockouts,
chimeras, and heterozygous specimens necessary for
rescuing inactive genes, minichromosome carriers, and
many others. Moreover, transfection is essential for the
analysis of factors that regulate gene expression and
intracellular signal transduction, as well as for insertional
mutagenesis and mapping.