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
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.
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.
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