Table 11-1 lists the proteins that catalyze critical recombination steps in bacteria as well as those that serve these same functions in eukaryotes (the budding yeast Saccharomyces cerevisiae is the best-understood example).These proteins provide activities needed to complete important steps in the DSB-repair pathway. In addition to these dedicated recombination proteins, DNA polymerases, ssDNA-binding proteins, topoisomerases, and ligases also have critical roles in the process of genetic exchange