Asked in Genetics

Can you summarize DNA replication?


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some teacher out there needs to answer this now

Watson and Crick developed a model for the secondary structure of DNA in 1953. DNA is a long linear polymer that has two major components: a backbone made up of sugar and phosphate groups and a series of nitrogenous bases that project from the backbone. These two long strands twist around each other and certain of the nitrogenous bases pair inside the spiral forming a double helix molecule. The structure is stabilized by hydrogen bonds that form between the bases called adenine and thymine and the bases guanine and cytosine. Watson and Crick suggested that the A-T and C-G pairing rules suggested a way for DNA to be copied prior to mitosis or meiosis. They suggested that the existing strands of DNA served as a template for the production of new strands, with bases being added to the new strands according to complimentary base-pairing rules. Each existing or old strand separated and served as a template for the synthesis of a new second strand so that each daughter DNA molecule consists of one old strand and one new strand, This is called semi-conservative replication and though other hypotheses were proposed experiments proved this hypothesis.

DNA Replication Summary1. Helicase separates antipolar strands forming a replication fork.

2. Binding proteins keep strands separate and topoisomerase relieves tension and removes kinks to allow the double helix molecule to continue to unravel.

3. Primase adds an RNA primer with an OH group to chemically bond with the first dNTP.

4. Polymerase III (Pol I-IV) synthesizes the leading strand in the 5'-3' direction. Antipolar lagging strand primer synthesizes RNA primer.

5. Pol III elongates primer; produces Okazaki fragment

6. Pol I excises RNA primer and fills the gap.

7. DNA Ligase links Okazaki fragments to form a continuos strand.

8. DNA Polymerase III can proofread.