Lecture 25

The Central Dogma of
Molecular Biology

DNA Replication
(Chapter 16)

BSCI105
P

RINCIPLES OF

BIOLOGY I

BSCI105
P

RINCIPLES OF

BIOLOGY I

4/8/15

1

4/8/15

BSCI105
P

RINCIPLES OF

BIOLOGY I

BSCI105
P

RINCIPLES OF

BIOLOGY I

Trivia Question!
How many base pairs of DNA are replicated every time a human cell divides? 1. 6 Hundred
2. 6 Thousand
3. 6 Million
4. 6 Trillion

Chromosome Structure
Prokaryotes
• One chromosome
• Circular
• ~ 5 million base pairs (E. coli )
Eukaryotes
• Many chromosomes
• Linear
• ~ 6000 million base pairs (humans)

2

DNA Replication
The Watson-Crick model of DNA immediately suggested a mechanism for replication: DNA Replication
Semi-conservative Replication
• One “parent” strand + one “daughter”
• New double helix – hybrid of old and new

BSCI105
P

RINCIPLES OF

BIOLOGY I

BSCI105
P

RINCIPLES OF

BIOLOGY I

4/8/15

3

Mechanism of
DNA Replication

DNA Replication
What do you need?
Enzymes!

BSCI105
P

RINCIPLES OF

BIOLOGY I

BSCI105
P

RINCIPLES OF

BIOLOGY I

4/8/15

4

Mechanism in E.coli

BSCI105
P

RINCIPLES OF

BIOLOGY I

BSCI105
P

RINCIPLES OF

BIOLOGY I

4/8/15

DNA Replication
Overview
3’
OH

T

5’

A

G

C

C

G

A

T

G

5’

C

OH
3’

5

BSCI105
P

RINCIPLES OF

BIOLOGY I

BSCI105
P

RINCIPLES OF

BIOLOGY I

4/8/15

DNA Replication
Overview
T

5’

G
C
A
G
OH
3’

DNA Replication
Overview
OH

T

5’

ATP

G
C
A
G
OH
3’

6

BSCI105
P

RINCIPLES OF

BIOLOGY I

BSCI105
P

RINCIPLES OF

BIOLOGY I

4/8/15

DNA Replication
Overview
OH

T

5’

G

OH

C

ATP
GTP

A
G
OH
3’

DNA Replication
Overview
3’
OH

T

5’
OH

G

OH

C

ATP
CTP
GTP

5’

A
G
OH
3’

7

BSCI105
P

RINCIPLES OF

BIOLOGY I

BSCI105
P

RINCIPLES OF

BIOLOGY I

4/8/15

DNA Replication
Overview
3’
OH

T

5’
OH

G

OH

C

ATP
CTP
GTP

5’

A
G
OH
3’

Polymerase

DNA Replication
Overview
3’
OH

T

5’
OH

G

OH

C

ATP
CTP
GTP

5’

A
G
OH
3’

8

BSCI105
P

RINCIPLES OF

BIOLOGY I

BSCI105
P

RINCIPLES OF

BIOLOGY I

4/8/15

DNA Replication
Overview
3’
OH