Molecular Basis of Inheritance

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Molecular Basis of Inheritance
2
Fredrick Griffith Experiment (TRANSFORMATION)
Mixture of heat-killed S cells and living R
cells
EXPERIMENT
Living R cells (control)
Living S cells (control)
Heat-killed S cells (control)
RESULTS
Mouse dies
Mouse healthy
Mouse dies
Mouse healthy
Living S cells
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Hershey and Chase Experiment
EXPERIMENT
Empty protein shell
Radioactivity (phage protein)
in liquid
Radioactive protein
Phage
Bacterial cell
DNA
Batch 1 radioactive sulfur (35S)
Phage DNA
Centrifuge
Pellet (bacterial cells and contents)
Radioactive DNA
Batch 2 radioactive phosphorus (32P)
Centrifuge
Radioactivity (phage DNA) in pellet
Pellet
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Watson and Crick
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Wilkins and Franklin
(a) Rosalind Franklin
(b) Franklins X-ray diffraction
photograph of DNA
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DNA Structure
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Sugarphosphate backbone
5? end
Nitrogenous bases
Thymine (T)
Adenine (A)
Cytosine (C)
DNA nucleotide
Phosphate
Sugar (deoxyribose) 3? end
Guanine (G)
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5? end
Hydrogen bond
3? end
1 nm
3.4 nm
3? end
0.34 nm
5? end
(c) Space-filling model
(b) Partial chemical structure
(a) Key features of DNA structure
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DNA Replication Basics
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DNA Replication Basics
A
T
C
G
T
A
T
A
C
G
(a) Parent molecule
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DNA Replication Basics
A
T
T
A
C
G
G
C
A
T
A
T
T
T
A
A
C
C
G
G
(b) Separation of strands
(a) Parent molecule
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DNA Replication Basics
A
A
T
T
A
T
T
A
C
C
G
G
G
C
G
C
A
T
A
A
T
A
T
T
T
T
A
T
T
A
A
A
C
C
G
C
C
G
G
G
(c) Daughter DNA molecules, each consisting of
one parental strand and one new strand
(b) Separation of strands
(a) Parent molecule
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Semiconservative replication
First replication
Second replication
Parent cell
(a) Conservative model
(b) Semiconserva- tive model
(c) Dispersive model
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DNA replication (the long version)
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Replication Bubbles and Forks
Origin of replication
Double-stranded DNA molecule
Parental (template) strand
Daughter (new) strand
0.25 µm
Replication fork
Bubble
Two daughter DNA molecules
(b) Origins of replication in eukaryotes
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DNA replication-Elongation
Primase
Single-strand binding proteins
3?
Topoisomerase
5?
3?
RNA primer
5?
5?
3?
Helicase
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New strand 5? end
Template strand 3? end
5? end
3? end
Sugar
T
A
A
T
Base
Phosphate
C
G
G
C
G
G
C
C
DNA polymerase
3? end
A
A
T
T
3? end
C
C
Pyrophosphate
Nucleoside triphosphate
5? end
5? end
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Leading Strandcontinuous synthesis5 to 3
Overview
Origin of replication
Leading strand
Lagging strand
Primer
Leading strand
Lagging strand
Overall directions of replication
Origin of replication
3?
5?
RNA primer
5?
Sliding clamp
3?
5?
DNA poll III
Parental DNA
3?
5?
5?
3?
5?
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Overview
Origin of replication
Leading strand
Lagging strand
Primer
Leading strand
Lagging strand
Overall directions of replication
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Origin of replication
3?
5?
RNA primer
5?
Sliding clamp
3?
5?
DNA pol III
Parental DNA
3?
5?
5?
Leading Strandcontinuous synthesis5 to 3
3?
5?
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Lagging StrandDiscontinuous synthesis
Overview
Origin of replication
Lagging strand
Leading strand
Lagging strand
2
1
Leading strand
Overall directions of replication
5?
3?
3?
5?
Template strand
RNA primer
3?
5?
3?
1
5?
3?
Okazaki fragment
5?
3?
1
5?
5?
3?
3?
2
5?
1
5?
3?
3?
5?
1
2
5?
3?
3?
5?
1
2
Overview slide
Overall direction of replication
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Lagging StrandDiscontinuous synthesisStep-by-S
tep
3?
5?
3?
5?
Template strand
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Lagging StrandDiscontinuous synthesisStep-by-S
tep
3?
5?
3?
5?
Template strand
3?
5?
3?
RNA primer
1
5?
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Lagging StrandDiscontinuous synthesisStep-by-S
tep
3?
5?
3?
5?
Template strand
3?
5?
3?
RNA primer
1
5?
3?
Okazaki fragment
5?
3?
1
5?
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Lagging StrandDiscontinuous synthesisStep-by-S
tep
3?
5?
3?
5?
Template strand
3?
5?
3?
RNA primer
1
5?
3?
Okazaki fragment
5?
3?
1
5?
5?
3?
3?
2
5?
1
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Lagging StrandDiscontinuous synthesisStep-by-S
tep
3?
5?
3?
5?
Template strand
3?
5?
3?
RNA primer
1
5?
3?
Okazaki fragment
5?
3?
1
5?
5?
3?
3?
2
5?
1
5?
3?
3?
5?
1
2
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Lagging StrandDiscontinuous synthesisStep-by-S
tep
3?
5?
3?
5?
Template strand
3?
5?
3?
RNA primer
1
5?
3?
Okazaki fragment
5?
3?
1
5?
5?
3?
3?
2
5?
1
5?
3?
3?
5?
1
2
5?
3?
3?
5?
1
2
Overall direction of replication
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Overview
Origin of replication
Lagging strand
Leading strand
Leading strand
Lagging strand
Single-strand binding protein
Overall directions of replication
Helicase
Leading strand
DNA pol III
5?
3?
3?
Primer
Primase
5?
Parental DNA
3?
Lagging strand
DNA pol III
5?
DNA pol I
DNA ligase
4
3?
5?
3
1
2
3?
5?
Events on Leading and Lagging strands shown
together
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Know this information !
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Errors in DNA sequence

• Mismatch repair
• DNA polymerase has proofreading capabilities
• Excision repair

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Excision repair
Nuclease
DNA polymerase
DNA ligase
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Molecular Basis of Inheritance

• Movie Review

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DNA replication movie-1
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DNA replication movie -2
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Leading Strand Movie
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Lagging Strand movie
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Replication Overview movie
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Overview
Origin of replication
Lagging strand
Leading strand
Leading strand
Lagging strand
Single-strand binding protein
Overall directions of replication
Helicase
Leading strand
DNA pol III
5?
3?
3?
Primer
Primase
5?
Parental DNA
3?
Lagging strand
DNA pol III
5?
DNA pol I
DNA ligase
4
3?
5?
3
1
2
3?
5?
Events on Leading and Lagging strands shown
together