DNA Polymerases Require a Primer to Initiate Replication

Analogous to RNA, DNA is synthesized from deoxynucleo-side 5'-triphosphate precursors (dNTPs). Also like RNA synthesis, DNA synthesis always proceeds in the 5'n3'

direction because chain growth results from formation of a phosphoester bond between the 3' oxygen of a growing strand and the a phosphate of a dNTP (see Figure 4-9). As discussed earlier, an RNA polymerase can find an appropriate transcription start site on duplex DNA and initiate the synthesis of an RNA complementary to the template DNA strand (see Figure 4-10). In contrast, DNA polymerases cannot initiate chain synthesis de novo; instead, they require a short, preexisting RNA or DNA strand, called a primer, to begin chain growth. With a primer base-paired to the template strand, a DNA polymerase adds deoxynucleotides to the free hydroxyl group at the 3' end of the primer as directed by the sequence of the template strand:


Was this article helpful?

0 0
10 Ways To Fight Off Cancer

10 Ways To Fight Off Cancer

Learning About 10 Ways Fight Off Cancer Can Have Amazing Benefits For Your Life The Best Tips On How To Keep This Killer At Bay Discovering that you or a loved one has cancer can be utterly terrifying. All the same, once you comprehend the causes of cancer and learn how to reverse those causes, you or your loved one may have more than a fighting chance of beating out cancer.

Get My Free Ebook

Post a comment