12.

Concerning the catalytic properties of DNA polymerase I of E. coli:

• a. 3' -> 5' exonuclease activity is used to proofread its own base incorporation errors.
• b. 5' -> 3' exonuclease activity is used to proofread its own base incorporation errors.
• c. Synthesis of DNA by ``nick-translation'' requires an RNA primer.
• d. The enzyme displays unlimited processivity.
• e. The enzyme displays sequence-specific endonuclease activity.