1. DNA
Structure
and
Replication

2. Transformation:
Robert Griffith (1928)

3. DNA is the
Transformer:
Avery (1944)

4. Chromosomes
and DNA

5. DNA has 4 Bases

6. Four DNA Bases
Adenine
Thymine
NH2
N
H 3C
N
NH
Guanine
N
NH
NH
NH
O
N
O
Cytosine
NH2
NH
N
O
N
NH2
NH
O

7. The Sugar
HO
OH
O
OH
Deoxyribose

8. The Nucleotides
A
O
HO
NH2
P
N
C
N
O
N
O
N
O
HO
OH
P
HO
P
N
O
O
OH
OH
T
O
G
O
N
O
OH
O
NH2
N
N
O
NH
O
H 3C
NH
O
N
NH2
HO
P
OH
O
N
O
OH
OH
OH
O

9. Adenine pairs with Thymine
Hydrogen
Bonding

10. Guanine pairs with Cytosine
Hydrogen
Bonding

11. DNA

12. Genes and Base Pairs:
A Comparison
Genes
(estimated)
Base Pairs
Yeast
6,000
12 million
Round Worm
19,000
99 million
Mouse
40,000
3 billion
Fruit Fly
13,600
165 million
Human
40,000
3 billion
Species
(Saccharomyces cerevisiae)
(Caenorhabditis elegans)
(Mus musculus)
(Drosophila melanogaster)
(Homo sapiens)

13. The
“Central Dogma”

14. Possible Modes of DNA Replication

15. Replication: 5’ to 3’ Direction ONLY
Continuous replication
on one strand
Discontinuous replication
on one strand

16. DNA Replication is
Catalyzed by Enzymes

17. DNA Polymerase Adds Complementary Bases

18. DNA Polymerase Sees Errors

19. DNA Polymerase Repairs Errors