C2005/F2401 '09 Outline for Lecture #11 Last update/posting 10/13/09 04:25 PM

I.  Details of DNA Structure

    A. Two Strands in helix are antiparallel

    B. Helix is held together by base stacking as well as base pairing

    C.  DNA is super coiled -- the double helix is folded up on itself

II. "Non-genetical" Implications of Structure

    A. Denaturation -- taking the 2 complementary strands ("Watson & Crick") apart

    B. Temperature at which DNA denatures (T_m) is proportional to % G+ C in the DNA

    C. Renaturation -- putting "Watson & Crick" back together

    D. Hybridization -- pairing up a "Watson" from one molecule with a "Crick" from another molecule

III. "Genetical" Implications -- How does DNA Replicate?

    A. Meselson-Stahl Experiment -- How does DNA serve as its own template?

        1. The possibilities -- conservative, semi-conservative & dispersive replication

        2. The experimental Procedure -- equilibrium density centrifugation

        3. The results

    B. Energy Considerations -- where does energy come from to drive polymerization of nucleotides?

    C. Enzymes & Chain Growth -- anything not finished in this lecture will be done in lecture 12.

        1. All new chains grow 5' to 3'; all templates are read 3' to 5'.

        2. Discontinuous Synthesis & ligase -- events at replication fork -- leading & lagging strands

        3. Bi-directional Replication -- 2 forks/origin

        4. RNA Primers & primase

The DNA story will be continued in Lecture #12 -- Wrap up of anything above we don't get to, and then PCR, a practical application of the need for primers. After PCR, on to "How does DNA determine protein sequence?"