Today’s Outline
• DNA and DNA Replication Review
– Leading Strand vs. Lagging Strand
– DNA Pol I vs. DNA Pol III
• Telomeres
• Molecular Sculpting
– DNA Replication
– PCR
• What’s Due?
– StudyNotes 7 is due on Thursday Mar 21
– HW # 5 and is due on Tuesday Mar 26.
– StudyNotes 8a is due on Tuesday Mar 26.
hydrogen bonds
5’ carbon
5’ carbon
3’ carbon
3’ carbon
A DNA Double Helix has a regular, repeated structure
DNA Polymerase III
Adds dNTPs to the newly synthesized strand on the
leading strand. Adds to the 3’ end of a ribose.
DNA Polymerase I
DNA Primase creates primers (red) that are RNA
molecules. DNA Pol I replaces the RNA nucleotides
with DNA nucleotides.
5
Ends of parental
DNA strands
Leading strand
Lagging strand
3
3
5
Last fragment
Previous fragment
Lagging strand RNA primer
5
3
Parental strand
Removal of primers and
replacement with DNA
where a 3 end is available
DNA Pol1 Can only add nucleotides to the
3’ end of existing DNA.
5
3
Telomeres protect an organism’s
genes from being eroded during
successive rounds of DNA
replication. In humans the
sequence TTAGGG is repeated
between 100 and 1000 times.
Second round
of replication
5
New leading strand 3
New lagging strand 5
3
Further rounds
of replication
Shorter and shorter daughter molecules
Molecular Sculpting
Two Models:
1. DNA Replication – must include:
– Helicase, topoisomerase, single strand binding
proteins, DNA primase, the sliding clamp, DNA pol
I, DNA pol III and ligase.
– Okazaki fragments, RNA primers, leading strand,
lagging strand, nucleotides and free dNTPs.
2. Polymerase Chain Reaction – must include:
– Three panels: denaturing, annealing and
extending.
– DNA, forward and reverse DNA primers, taq
polymerase, dNTPs.