Mutations are heritable changes in an organism's genome.
On an evolutionary scale, mutations are the source of variation upon which natural selection works. On a human scale, mutations give rise to birth detects, genetic diseases, and cancer. Using the bacterium Escherichia coli as a model system, my laboratory employs genetic and molecular techniques to investigate the molecular mechanisms by which mutations arise spontaneously and as a result of DNA damage. We found that a novel type of recombination-dependent mutational process occurs in cells under selection, but the process is not truly adaptive because it also gives rise to nonselected mutations. We are investigating the molecular mechanism of recombination-dependent mutation, and are determining its general importance.