Biology 1201A Lecture 6: Lecture-6-Notes
10 Dec 2015
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In 1972, douglas l. brutlag and arthur kornberg, of stanford, proposed the proofreading mechanism, which is dependent on the ability of dna polymerases to back up and remove mismatched nucleotides from a. The dna polymerases can only add nucleotides to the growing chain, once the most recently added base is correctly paired with its complementary base on the template strand. If the correct pairs are not formed, the fully stabilizing hydrogen bonds will not form. When a newly added nucleotide is mismatched, the dna polymerase reverses and uses a built in de-oxyribonuclease to remove the newly added incorrect nucleotide. Once this has been done, the enzyme resumes working forward, now inserting the correct nucleotide. 1 million nucleotides assembled in the test tube, but without the proofreading activity of this enzyme, the error rate increases to 1 mistake for every 1000 to 10 000 nucleotides assembled.
