In transformation, bacterial cells which are competent (have the ability
to absorb DNA) take in foreign DNA and incorporate it as their own.
Griffith showed this to be the case with Streptococcus pneumoniae,
and Avery et al. would later demonstrate that DNA was the
transforming principle. This phenomenon rarely happens naturally,
and the extracellular DNA must be compatible to that of the recipient for
recombination to occur.