DNA Replication and Synthesis

    I.  DNA Replication:

        Semi conservative model:  something old:  parental strand;
                                                    something new:  newly synthesized strand.

        DNA Polymerase and DNA ligase together are responsible for DNA replication, plus some other
        enzymatic factors.

II.  The Process of DNA Replication:

    1.  Origin of Replication:  DNA replication begins at specific sites where the two parental strands of
         DNA separate to form a replication fork (bubble).

    2.  Elongation of DNA:  catalyzed by DNA polymerase.

    3.  The Source of Energy of DNA replication:  ATP

    4.  Direction of DNA replication:  The two DNA strands are antiparallel.

        Leading strand:  DNA polymerase nestles in the replication fork and moves along the template strand as the fork
                                    progresses.  The DNA strand made by this mechanism is called leading strand.

        Lagging strand: DNA polymerase works along the template away from the replication fork, the DNA synthesized in
                                   this direction is called lagging strand.

        Okazaki fragments:  The lagging strand is first synthesized as a series of segments.  These segments are called Okazaki
                                           fragment.  DNA ligase joins the okazaki fragments into a single lagging strand.

III.  Enzymes (nuclease) proofread DNA during its replication and repair damages in existing DNA.
 
 

 IV. Heritable mutations:  germ-line cell mutations are heritable.

 V.  Value of mutations (mistakes):  Evolutionary adaptation.