1. We will focus on these 3 classic experiments highlighted in this chapter……
Griffith (Frederick)
Hershey and Chase (Alfred and Martha)
Meselsen and Stahl (Matt and Frank)

2. There are unknown heritable substances…
Griffith
There are unknown heritable substances…
Turned to a bacterial pathogen…Streptococcus pneumoniae
Is it gram positive or negative?

3. Work by Avery identified the transforming substance as DNA
Figure 13.2
Experiment
Mixture of
heat-killed
S cells and
living R cells
Living
S cells
(control)
Living
R cells
(control)
Heat-killed
S cells
(control)
Figure 13.2 Inquiry: Can a genetic trait be transferred between different bacterial strains?
Results
Mouse dies
Mouse healthy
Mouse healthy
Mouse dies
Work by Avery identified the transforming substance as DNA
Living S cells

4. Transformation-did not really understand mechanism
Can we do this-pick up DNA from our environment?

5. Hershey and Chase (1952)
Their work pointed to DNA rather than proteins…
Bacteriophages what are they???? (worked with one called T2)

6. Some phages grown in media for a couple hrs with radioactive Sulphur…(which should be incorporated into some proteins Methionine, Cysteine)
Other phages grown in media for a couple hrs with radioactive Phosphorus….(which should be incorporated into DNA)

7. Batch 1: Radioactive sulfur (35S) in phage protein
Figure 13.4
Experiment
Batch 1: Radioactive sulfur (35S) in phage protein 1
Labeled phages
infect cells. 2
Agitation frees outside
phage parts from cells. 3
Centrifuged cells
form a pellet.
Radioactive
protein 4
Radioactivity
(phage protein)
found in liquid
Centrifuge
Pellet
Batch 2: Radioactive phosphorus (32P) in phage DNA
Radioactive
DNA
Figure 13.4 Inquiry: Is protein or DNA the genetic material of phage T2?
Centrifuge 4
Radioactivity (phage
DNA) found in pellet
Pellet 7

8. Watson-Crick Model predicted….
Each of two daughter molecules would have one parental strand and one newly made!
Meselson and Stahl-clever experiment…What did they do??

9. Experiment Bacteria cultured in medium with 15N (heavy isotope)
Figure 13.11
Experiment 1
Bacteria
cultured in
medium
with 15N
(heavy
isotope) 2
Bacteria
transferred
to medium
with 14N
(lighter
isotope)
Results 3
DNA sample
centrifuged
after first
replication 4
DNA sample
centrifuged
after second
replication
Less
dense
More
dense
Conclusion
Predictions:
First replication
Second replication
Conservative
model
Figure Inquiry: Does DNA replication follow the conservative, semiconservative, or dispersive model?
Semiconservative
model
Dispersive
model 9

10. Figure 13.1
Watson and Crick
Figure 13.1 How was the structure of DNA determined?

11. What do these terms refer to…
How does this replication thing work??
origin of replication
helicase
topoisomerase
replication fork
primase and the RNA primer
single stranded binding proteins
DNA polymerase
Search online for stronger and weaker video clips-which one is the very best and the very worst?
me the links to your very best and worst (with your group members names)
Jot down on the board enough of the web address that we can distinguish which ones are the same

12. 1 2 5 end 3 end 3 end 5 end T A G C C G A T Figure 13.7b
Figure 13.7b The double helix (part 2: chemical structure) A T
3 end
5 end 12

13. Single-strand binding proteins
Figure 13.12
Primase
Topoisomerase 3
RNA
primer 5 3 5
Replication
fork 3
Helicase 5
Single-strand binding
proteins

14. Overall directions of replication
Figure 13.15
Overview
Leading
strand
Origin of replication
Lagging
strand
Primer
Leading
strand
Lagging strand
Overall
directions
of replication
Origin of replication 3 5 5
RNA primer 3 3
Sliding clamp
DNA pol III
Parental DNA
Figure Synthesis of the leading strand during DNA replication 5 3 5 5
Continuous elongation
in the 5 to 3 direction 3 3 5 14

15. Overall directions of replication
Figure 13.16a
Overview
Lagging
strand
Origin of replication
Leading
strand
Lagging
strand
Leading
strand
Overall directions
of replication
Figure 13.16a Synthesis of the lagging strand (part 1)
What is going to latch on at #1? 15

16. Primase makes RNA primer. Template strand 1 3 5 3 5
Figure 13.16b-1 1
Primase makes
RNA primer. 3 5 3
Template
strand 5
Figure 13.16b-1 Synthesis of the lagging strand (part 2, step 1) 16

17. Primase makes RNA primer. Template strand RNA primer DNA pol III
Figure 13.16b-2 1
Primase makes
RNA primer. 3 5 3
Template
strand 5
RNA primer
for fragment 1 2
DNA pol III
makes Okazaki
fragment 1. 3 5 3 5
Figure 13.16b-2 Synthesis of the lagging strand (part 2, step 2) 17

18. Where is DNA pol III going to go next??
Figure 13.16b-3 1
Primase makes
RNA primer. 3 5 3
Template
strand 5
RNA primer
for fragment 1 2
DNA pol III
makes Okazaki
fragment 1. 3 5 3 5
Figure 13.16b-3 Synthesis of the lagging strand (part 2, step 3) 3
DNA pol III
detaches. 3
Okazaki
fragment 1 5 3 5
Where is DNA pol III going to go next?? 18

19. Figure 13.16c-1
RNA primer for fragment 2
Okazaki
fragment 2 5 4
DNA pol III
makes Okazaki
fragment 2. 3 3 5
Now you have all these bits what has to happen next? And who does that?
Figure 13.16c-1 Synthesis of the lagging strand (part 3, step 1) 19

20. RNA primer for fragment 2
Figure 13.16c-2
RNA primer for fragment 2
Okazaki
fragment 2 5 4
DNA pol III
makes Okazaki
fragment 2. 3 3 5 5 5
DNA pol I
replaces RNA
with DNA. 3 3 5
Figure 13.16c-2 Synthesis of the lagging strand (part 3, step 2) 20

21. RNA primer for fragment 2
Figure 13.16c-3
RNA primer for fragment 2
Okazaki
fragment 2 5 4
DNA pol III
makes Okazaki
fragment 2. 3 3 5 5 5
DNA pol I
replaces RNA
with DNA. 3 3 5 6
DNA ligase forms
bonds between
DNA fragments.
Figure 13.16c-3 Synthesis of the lagging strand (part 3, step 3) 5 3 3 5
Overall direction of replication 21

22. Overall directions of replication
Figure 13.16
Overview
Lagging
strand
Origin of replication
Leading
strand
Lagging
strand
Leading
strand
RNA primer
for fragment 2
Overall directions
of replication
Okazaki
fragment 2 5 4
DNA pol III
makes Okazaki
fragment 2. 3 1
Primase makes
RNA primer. 3 5 3 3
Template
strand 5 5 5 5
DNA pol I
replaces RNA
with DNA. 3
RNA primer
for fragment 1 2
DNA pol III
makes Okazaki
fragment 1. 3
Figure Synthesis of the lagging strand 5 3 3 5 6
DNA ligase forms
bonds between
DNA fragments. 5 5 3 3
DNA pol III
detaches. 3
Okazaki
fragment 1 5 3 5 3 5
Overall direction of replication 22

23. Leading strand template Single-strand binding proteins Leading strand
Figure 13.17
Overview
Origin of replication
Leading strand
template
Leading strand
Lagging
strand
Single-strand
binding proteins
Lagging strand
Leading strand
Overall directions
of replication
Leading strand
Helicase
DNA pol III 5 3
Primer 5 3
Primase 3
Parental DNA
Lagging strand
DNA pol III
Figure A summary of bacterial DNA replication 5
Lagging strand
template 3
DNA pol I
DNA ligase 5 3 5 23

24. Overall directions of replication
Figure 13.17a
Overview
Origin of replication
Leading strand
Lagging
strand
Lagging strand
Leading strand
Figure 13.17a A summary of bacterial DNA replication (part 1)
Overall directions
of replication 24

25. Leading strand template Single-strand binding proteins Leading strand
Figure 13.17b
Leading strand
template
Single-strand
binding proteins
Leading strand
Helicase
DNA pol III 5
Primer 3 5
Primase 3 3
Figure 13.17b A summary of bacterial DNA replication (part 2)
Parental DNA
Lagging strand
template 25

26. Lagging strand DNA pol III 5 3 DNA pol I DNA ligase 5 3 5
Figure 13.17c
Lagging strand
DNA pol III 5 3
DNA pol I
DNA ligase 5 3 5
Figure 13.17c A summary of bacterial DNA replication (part 3) 26

27. DNA poly- merase Pyro- phosphate
Figure 13.14
New strand
Template strand 5 3 5 3
Sugar A T A T
Base
Phosphate C G C G
DNA
poly-
merase G C G C 3 A T A T
Figure Addition of a nucleotide to a DNA strand P P P P i P C 3 C
Pyro-
phosphate
Nucleotide 5 5 2 P i 27

28. Question 1.
True of Leading strand, Lagging strand, or Both????
Daughter strand elongates away from replication fork
Synthesizes 5’ to 3’
Multiple primers needed
Made in segments
Made continuously
Daughter strand elongates toward replication fork

29. True of Leading strand, Lagging strand, or Both????
Daughter strand elongates away from replication fork Lag
Synthesizes 5’ to 3’ Both
Multiple primers needed Lagg
Made in segments Lag
Made continuously Lead
Daughter strand elongates toward replication fork from Lead

30. Question 2. The diagram below shows a replication bubble with synthesis of the leading and lagging strands on both sides of the bubble. The parental DNA is shown in dark blue, the newly synthesized DNA is light blue, and the RNA primers associated with each strand are red. The origin of replication is indicated by the black dots on the parental strands.
Rank the primers in the order they were produced. If two primers were produced at the same time, overlap them.

31. Question 3. The lagging strand is synthesized as a series of segments called Okazaki fragments Fragment A is the most recently synthesized and Fragment B will be synthesized next in the space between primers A and B.
-----Start DNA polymerase III binds to 3’ end of primer B
A. DNA polymerase I replaces primer with DNA
B. DNA polymerase I binds to 5’ end of primer A
C. DNA polymerase III moves 5’ to 3’ adding DNA nucleotides to primer B
D. DNA ligase links fragments A and B

32. In an analysis of the nucleotide composition of DNA, which of the following will be found?
A = G and C = T
G + C = T + A
A = C
A + C = G + T

33. Cytosine makes up 42% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be thymine?
31%
42% 8%
16%
It cannot be determined from the information provided.