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![Page 1: DNA The Molecule of Life. Overview: Lifes Operating Instructions 1953 –James Watson and Francis Crick –Structure of the molecule of inheritance –Deoxyribonucleic.](https://reader036.fdocuments.in/reader036/viewer/2022081516/55149e2f550346b2598b59ac/html5/thumbnails/1.jpg)
DNA
The Molecule of Life
![Page 2: DNA The Molecule of Life. Overview: Lifes Operating Instructions 1953 –James Watson and Francis Crick –Structure of the molecule of inheritance –Deoxyribonucleic.](https://reader036.fdocuments.in/reader036/viewer/2022081516/55149e2f550346b2598b59ac/html5/thumbnails/2.jpg)
Overview: Life’s Operating Instructions• 1953
– James Watson and Francis Crick
– Structure of the molecule of inheritance
– Deoxyribonucleic acid
• Rosalind Franklin– Used X-ray
crystalography to take the first picture of the molecule
© 2011 Pearson Education, Inc.
![Page 3: DNA The Molecule of Life. Overview: Lifes Operating Instructions 1953 –James Watson and Francis Crick –Structure of the molecule of inheritance –Deoxyribonucleic.](https://reader036.fdocuments.in/reader036/viewer/2022081516/55149e2f550346b2598b59ac/html5/thumbnails/3.jpg)
Figure 16.4-1
Bacterial cell
Phage
Batch 1:Radioactivesulfur(35S)
DNA
Batch 2:Radioactivephosphorus(32P)
RadioactiveDNA
EXPERIMENTRadioactiveprotein
In 1952, Alfred Hershey and Martha Chase performed experiments showing that DNA is the genetic material of a phage known as T2.
![Page 4: DNA The Molecule of Life. Overview: Lifes Operating Instructions 1953 –James Watson and Francis Crick –Structure of the molecule of inheritance –Deoxyribonucleic.](https://reader036.fdocuments.in/reader036/viewer/2022081516/55149e2f550346b2598b59ac/html5/thumbnails/4.jpg)
Figure 16.4-2
Bacterial cell
Phage
Batch 1:Radioactivesulfur(35S)
Radioactiveprotein
DNA
Batch 2:Radioactivephosphorus(32P)
RadioactiveDNA
Emptyproteinshell
PhageDNA
EXPERIMENT
![Page 5: DNA The Molecule of Life. Overview: Lifes Operating Instructions 1953 –James Watson and Francis Crick –Structure of the molecule of inheritance –Deoxyribonucleic.](https://reader036.fdocuments.in/reader036/viewer/2022081516/55149e2f550346b2598b59ac/html5/thumbnails/5.jpg)
Figure 16.4-3
Bacterial cell
Phage
Batch 1:Radioactivesulfur(35S)
Radioactiveprotein
DNA
Batch 2:Radioactivephosphorus(32P)
RadioactiveDNA
Emptyproteinshell
PhageDNA
Centrifuge
Centrifuge
Radioactivity(phage protein)in liquid
Pellet (bacterialcells and contents)
PelletRadioactivity(phage DNA)in pellet
EXPERIMENT
![Page 6: DNA The Molecule of Life. Overview: Lifes Operating Instructions 1953 –James Watson and Francis Crick –Structure of the molecule of inheritance –Deoxyribonucleic.](https://reader036.fdocuments.in/reader036/viewer/2022081516/55149e2f550346b2598b59ac/html5/thumbnails/6.jpg)
Figure 16.7
3.4 nm
1 nm
0.34 nm
Hydrogen bond
(a) Key features ofDNA structure
Space-fillingmodel
(c)(b) Partial chemical structure
3 end
5 end
3 end
5 end
T
T
A
A
G
G
C
C
C
C
C
C
C
C
C
C
C
G
G
G
G
G
G
G
G
G
T
T
T
T
T
T
A
A
A
A
A
A
![Page 7: DNA The Molecule of Life. Overview: Lifes Operating Instructions 1953 –James Watson and Francis Crick –Structure of the molecule of inheritance –Deoxyribonucleic.](https://reader036.fdocuments.in/reader036/viewer/2022081516/55149e2f550346b2598b59ac/html5/thumbnails/7.jpg)
Figure 16.UN01
Purine purine: too wide
Pyrimidine pyrimidine: too narrow
Purine pyrimidine: widthconsistent with X-ray data
![Page 8: DNA The Molecule of Life. Overview: Lifes Operating Instructions 1953 –James Watson and Francis Crick –Structure of the molecule of inheritance –Deoxyribonucleic.](https://reader036.fdocuments.in/reader036/viewer/2022081516/55149e2f550346b2598b59ac/html5/thumbnails/8.jpg)
• Erwin Chargaff – measured the amount of each base (ATCG) in segments of DNA from different organisms
• Two findings became known as Chargaff’s rules– The base composition of DNA varies between species– In any species the number of A and T bases are equal
and the number of G and C bases are equal
© 2011 Pearson Education, Inc.
![Page 9: DNA The Molecule of Life. Overview: Lifes Operating Instructions 1953 –James Watson and Francis Crick –Structure of the molecule of inheritance –Deoxyribonucleic.](https://reader036.fdocuments.in/reader036/viewer/2022081516/55149e2f550346b2598b59ac/html5/thumbnails/9.jpg)
Figure 16.8
Sugar
Sugar
Sugar
Sugar
Adenine (A) Thymine (T)
Guanine (G) Cytosine (C)
![Page 10: DNA The Molecule of Life. Overview: Lifes Operating Instructions 1953 –James Watson and Francis Crick –Structure of the molecule of inheritance –Deoxyribonucleic.](https://reader036.fdocuments.in/reader036/viewer/2022081516/55149e2f550346b2598b59ac/html5/thumbnails/10.jpg)
Figure 16.9-1
(a) Parent molecule
A
A
A
T
T
T
C
C
G
G
![Page 11: DNA The Molecule of Life. Overview: Lifes Operating Instructions 1953 –James Watson and Francis Crick –Structure of the molecule of inheritance –Deoxyribonucleic.](https://reader036.fdocuments.in/reader036/viewer/2022081516/55149e2f550346b2598b59ac/html5/thumbnails/11.jpg)
Figure 16.9-2
(a) Parent molecule (b) Separation ofstrands
A
A
A
A
A
A
T
T
T
T
T
T
C
C
C
C
G
G
G
G
![Page 12: DNA The Molecule of Life. Overview: Lifes Operating Instructions 1953 –James Watson and Francis Crick –Structure of the molecule of inheritance –Deoxyribonucleic.](https://reader036.fdocuments.in/reader036/viewer/2022081516/55149e2f550346b2598b59ac/html5/thumbnails/12.jpg)
Figure 16.9-3
(a) Parent molecule (b) Separation ofstrands
(c)“Daughter” DNA molecules,each consisting of oneparental strand and onenew strand = semi-conservative
A
A
A
A
A
A
A
A
A
A
A
A
T
T
T
T
T
T
T
T
T
T
T
T
C
C
C
C
C
C
C
C
G
G
G
G
G
G
G
G
![Page 13: DNA The Molecule of Life. Overview: Lifes Operating Instructions 1953 –James Watson and Francis Crick –Structure of the molecule of inheritance –Deoxyribonucleic.](https://reader036.fdocuments.in/reader036/viewer/2022081516/55149e2f550346b2598b59ac/html5/thumbnails/13.jpg)
DNA Replication
• Replication proceeds in both directions from the origins of replication.
• replication fork - a Y-shaped region where new DNA strands are elongating
• Helicases - enzymes that untwist the double helix at the replication forks
• Single-strand binding proteins bind to and stabilize single-stranded DNA
• Topoisomerase – enzyme that corrects “overwinding” ahead of replication forks by breaking, swiveling, and rejoining DNA strands
© 2011 Pearson Education, Inc.
![Page 14: DNA The Molecule of Life. Overview: Lifes Operating Instructions 1953 –James Watson and Francis Crick –Structure of the molecule of inheritance –Deoxyribonucleic.](https://reader036.fdocuments.in/reader036/viewer/2022081516/55149e2f550346b2598b59ac/html5/thumbnails/14.jpg)
Figure 16.13
Topoisomerase
Primase
RNAprimer
Helicase
Single-strand bindingproteins
5
3
5
53
3
![Page 15: DNA The Molecule of Life. Overview: Lifes Operating Instructions 1953 –James Watson and Francis Crick –Structure of the molecule of inheritance –Deoxyribonucleic.](https://reader036.fdocuments.in/reader036/viewer/2022081516/55149e2f550346b2598b59ac/html5/thumbnails/15.jpg)
Synthesizing a New DNA Strand
• Enzymes called DNA polymerases catalyze the elongation of new DNA at a replication fork by adding to the 3’ end of an existing molecule.
• Most DNA polymerases require an RNA primer (primase) and a DNA template strand to build from.
• The rate of elongation is about 500 nucleotides per second in bacteria and 50 per second in human cells.
© 2011 Pearson Education, Inc.
![Page 16: DNA The Molecule of Life. Overview: Lifes Operating Instructions 1953 –James Watson and Francis Crick –Structure of the molecule of inheritance –Deoxyribonucleic.](https://reader036.fdocuments.in/reader036/viewer/2022081516/55149e2f550346b2598b59ac/html5/thumbnails/16.jpg)
Figure 16.14
New strand Template strand
Sugar
Phosphate Base
Nucleosidetriphosphate
DNApolymerase
Pyrophosphate
5
5
5
5
3
3
3
3
OH
OH
OH
P P i
2 P i
PP
P
A
A
A
A
T T
TT
C
C
C
C
C
C
G
G
G
G
Nucleotides are added as nucleoside triphosphate (i.e. dATP).
![Page 17: DNA The Molecule of Life. Overview: Lifes Operating Instructions 1953 –James Watson and Francis Crick –Structure of the molecule of inheritance –Deoxyribonucleic.](https://reader036.fdocuments.in/reader036/viewer/2022081516/55149e2f550346b2598b59ac/html5/thumbnails/17.jpg)
Figure 16.15
Leadingstrand
Laggingstrand
Overview
Origin of replication Laggingstrand
Leadingstrand
Primer
Overall directionsof replication
Origin of replication
RNA primer
Sliding clamp
DNA pol IIIParental DNA
35
5
33
5
3
5
3
5
3
5
DNA polymerase can only add to the 3’ end (5 3).
Leading Strand
Lagging Strand
Okasaki Fragments
DNA ligase
![Page 18: DNA The Molecule of Life. Overview: Lifes Operating Instructions 1953 –James Watson and Francis Crick –Structure of the molecule of inheritance –Deoxyribonucleic.](https://reader036.fdocuments.in/reader036/viewer/2022081516/55149e2f550346b2598b59ac/html5/thumbnails/18.jpg)
Figure 16.15a
Leadingstrand
Laggingstrand
Overview
Origin of replication Laggingstrand
Leadingstrand
Primer
Overall directionsof replication
![Page 19: DNA The Molecule of Life. Overview: Lifes Operating Instructions 1953 –James Watson and Francis Crick –Structure of the molecule of inheritance –Deoxyribonucleic.](https://reader036.fdocuments.in/reader036/viewer/2022081516/55149e2f550346b2598b59ac/html5/thumbnails/19.jpg)
Figure 16.16b-1
Templatestrand
3
35
5
![Page 20: DNA The Molecule of Life. Overview: Lifes Operating Instructions 1953 –James Watson and Francis Crick –Structure of the molecule of inheritance –Deoxyribonucleic.](https://reader036.fdocuments.in/reader036/viewer/2022081516/55149e2f550346b2598b59ac/html5/thumbnails/20.jpg)
Figure 16.16b-2
Templatestrand
RNA primerfor fragment 1
3
3
3
3
5
5
5
51
![Page 21: DNA The Molecule of Life. Overview: Lifes Operating Instructions 1953 –James Watson and Francis Crick –Structure of the molecule of inheritance –Deoxyribonucleic.](https://reader036.fdocuments.in/reader036/viewer/2022081516/55149e2f550346b2598b59ac/html5/thumbnails/21.jpg)
Figure 16.16b-3
Templatestrand
RNA primerfor fragment 1
Okazakifragment 1
3
3
3
3
3
3
5
5
5
5
5
5
1
1
![Page 22: DNA The Molecule of Life. Overview: Lifes Operating Instructions 1953 –James Watson and Francis Crick –Structure of the molecule of inheritance –Deoxyribonucleic.](https://reader036.fdocuments.in/reader036/viewer/2022081516/55149e2f550346b2598b59ac/html5/thumbnails/22.jpg)
Figure 16.16b-4
Templatestrand
RNA primerfor fragment 1
Okazakifragment 1
RNA primerfor fragment 2
Okazakifragment 2
3
3
3
3
3
3
3
3
5
5
5
5
5
55
5
2
1
1
1
![Page 23: DNA The Molecule of Life. Overview: Lifes Operating Instructions 1953 –James Watson and Francis Crick –Structure of the molecule of inheritance –Deoxyribonucleic.](https://reader036.fdocuments.in/reader036/viewer/2022081516/55149e2f550346b2598b59ac/html5/thumbnails/23.jpg)
Figure 16.16b-5
Templatestrand
RNA primerfor fragment 1
Okazakifragment 1
RNA primerfor fragment 2
Okazakifragment 2
3
3
3
3
3
3
3
3
3
3
3
5
5
5
5
5
55
55
55
2
21
1
1
1
![Page 24: DNA The Molecule of Life. Overview: Lifes Operating Instructions 1953 –James Watson and Francis Crick –Structure of the molecule of inheritance –Deoxyribonucleic.](https://reader036.fdocuments.in/reader036/viewer/2022081516/55149e2f550346b2598b59ac/html5/thumbnails/24.jpg)
Figure 16.16b-6
Templatestrand
RNA primerfor fragment 1
Okazakifragment 1
RNA primerfor fragment 2
Okazakifragment 2
Overall direction of replication
3
3
3
3
3
3
3
3
3
3
3
3
5
5
5
5
5
55
55
55
5
2
2
21
1
1
1
1
![Page 25: DNA The Molecule of Life. Overview: Lifes Operating Instructions 1953 –James Watson and Francis Crick –Structure of the molecule of inheritance –Deoxyribonucleic.](https://reader036.fdocuments.in/reader036/viewer/2022081516/55149e2f550346b2598b59ac/html5/thumbnails/25.jpg)
Figure 16.17
Overview
Leadingstrand
Origin of replication Lagging
strand
LeadingstrandLagging
strand Overall directionsof replicationLeading strand
DNA pol III
DNA pol III Lagging strand
DNA pol I DNA ligase
PrimerPrimase
ParentalDNA
5
5
5
5
5
33
3
333 2 1
4
![Page 26: DNA The Molecule of Life. Overview: Lifes Operating Instructions 1953 –James Watson and Francis Crick –Structure of the molecule of inheritance –Deoxyribonucleic.](https://reader036.fdocuments.in/reader036/viewer/2022081516/55149e2f550346b2598b59ac/html5/thumbnails/26.jpg)
Overview
Leadingstrand
Origin of replication Lagging
strand
LeadingstrandLagging
strand Overall directionsof replicationLeading strand
Primer
DNA pol III
DNA pol I
Lagging strand
DNA ligase5
5
5
33
3 34
2 1
Figure 16.17b
![Page 27: DNA The Molecule of Life. Overview: Lifes Operating Instructions 1953 –James Watson and Francis Crick –Structure of the molecule of inheritance –Deoxyribonucleic.](https://reader036.fdocuments.in/reader036/viewer/2022081516/55149e2f550346b2598b59ac/html5/thumbnails/27.jpg)
Figure 16.18
Parental DNA
DNA pol III
Leading strand
Connectingprotein
Helicase
Lagging strandDNA pol III
Laggingstrandtemplate
5
5
5
5
5
5
3 3
33
3
3
DNA Replication Complex
![Page 28: DNA The Molecule of Life. Overview: Lifes Operating Instructions 1953 –James Watson and Francis Crick –Structure of the molecule of inheritance –Deoxyribonucleic.](https://reader036.fdocuments.in/reader036/viewer/2022081516/55149e2f550346b2598b59ac/html5/thumbnails/28.jpg)
Figure 16.19
Nuclease
DNA polymerase
DNA ligase
5
5
5
5
5
5
5
5
3
3
3
3
3
3
3
3
Proofreading
Nucleotide Excision Repair
Hopefully:
DNA Polymerases edit the new strand as they move along the molecule = mismatch repair
If not:
Nucleotide Excision Repair
Nucleases