Post on 22-Dec-2015
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