Chapter 13DNA Replication

Figure 13.2

LivingS cells(control)

Mouse healthy

Results

Griffith

Mouse healthy Mouse dies

Living S cells

LivingR cells(control)

Heat-killedS cells(control)

Mixture ofheat-killedS cells andliving R cells

Mouse dies

Figure 13.4

Labeled phagesinfect cells.

Batch 1: Radioactive sulfur (35S) in phage protein

Hershey and Chase

Agitation frees outsidephage parts from cells.

Centrifuged cellsform a pellet.

Radioactivity(phage protein)found in liquid

Batch 2: Radioactive phosphorus (32P) in phage DNA

Radioactivity (phage DNA) found in pellet

Radioactiveprotein

RadioactiveDNA

Centrifuge

Centrifuge

Pellet

Pellet

1 2 3

4

4

You Must Know

• The structure of DNA.• Replication is semiconservative and occurs 5’

to 3’.• The roles of DNA polymerase, ligase, helicase,

and topoisomerase in replication.• The general difference between bacterial

chromosomes and eukaryotic chromosomes.

Video

DNA Replication Process [3D Animation]

semiconservative model of replication

(a) Parentalmolecule

T A

C G

CG

TA

TATA

T A

C G

CG

TA

T A

C G

CG

TA

TA

T A

C G

CG

TA

TA

(b) Separation of parentalstrands into templates

(c) Formation of newstrands complementaryto template strands

An E. coli cell that contains a single circular chromosome is allowed to replicated in 15N medium until of the DNA is labeled with 15N. One cell is removed and placed in 14N medium. The E coli is allowed to replicate until eight E-coli are formed.

Which of the following is true?

1. Some of the 15N DNA will be found in all eight cells.2. Some of the 15N DNA will be found in only four of the cells.3. Some of the 15N DNA will be found in only two of the cells.4. Some of the 15N DNA will be found in only one of the cells.

To explain your answer, draw the sequence of events that occurred.

3. Some of the 15N DNA will be found in only two of the cells.

Figure 13.17a

Origin of replication

Replication forkReplication fork

DNA replication in a prokaryotic cell

Double-strandedDNA molecule

Origin of replication

Replicationbubble

Replicationfork

Daughter(new) strandParental

(template) strand

Twodaughter DNAmolecules

Origins of replication in a eukaryotic cell

Origin ofreplication

Double-strandedDNA molecule

Daughter (new)strand

Parental (template)strand

Bubble Replication fork

Two daughter DNA molecules

DNA preparing to add new nucleotides

Replicationfork

5

5

5

3

3

3Topoisomerase

Helicase

Single-strand bindingproteins

Primase

RNAprimer

Parental DNA

5

3

53

DNA pol III

RNA primer

5

3

Origin of replicationDNA adding new nucleotides

5

3

5

3elongationin the 5 to 3 direction

53

Figure 13.14

New strand

Phosphate

Nucleotide dATP

5 3Template strand

Sugar

Base

5

3

A T

C G

AT

CG

CPP

P

Pyro-phosphate

DNA poly-

merase

P

P iP

i2

5

3

5 3

T

A T

C G

A

CG

C

Figure 13.15a

Origin of replication

Lagging strand

Laggingstrand

Overalldirections

of replication

Leadingstrand

Leadingstrand

Overview

Primer

Synthesis of the leading strand during DNA replication

Parental DNA

5

3

5

3

5

3

Continuous elongationin the 5 to 3 direction

53

53

DNA pol III

RNA primer

Sliding clamp

5

3

Origin of replication

Figure 13.16a

Lagging strand Lagging

strand

Overall directionsof replication

Overview

Okazaki fragments

Synthesis of the lagging strand

53

5

3 Primase makesRNA primer.

Templatestrand

1

RNA primerfor fragment 1

DNA pol IIImakes Okazakifragment 1.

53

5

32

Okazakifragment 1

DNA pol IIIdetaches.

5

35

33

RNA primer for fragment 2

Okazakifragment 2 DNA pol III

makes Okazakifragment 2.

5

35

3 4

Synthesis of the lagging strand

DNA pol Ireplaces RNAwith DNA.

5

35

3 5

DNA ligase formsbonds betweenDNA fragments.

5

35

3

56

A summary of DNA replication

3

5

Origin of replication

Lagging strand

Laggingstrand

Overall directionsof replication

Leading strand

Leading strand

Overview

53

5

3

Leading strand

Lagging strand

DNA ligaseDNA pol IDNA pol III

Primase

DNA pol III

Primer5

35

3

Lagging strandtemplate

Parental DNA

Helicase

Single-strandbinding proteins

Leading strandtemplate