F: Genetic Control
1 Introduction:1.1 Structure of DNA and RNA1.2 Base pairing1.3 DNA is the genetic material
2 DNA Replication:
3 Transcription: DNA to RNA:
4 Translation: mRNA to protein:4.1 Introduction4.2 The Genetic Code4.3 tRNAs4.4 Ribosomes4.5 Mechanism of translation
5 Mutations:
6 Conclusions and Overviews:
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Xavier DANIEL, Ph.D.A
F: Genetic ControlDNA Replication is semi-conservative
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Xavier DANIEL, Ph.D.A
Goals of this lesson
Watson and Crick’s notice
Three ways to replicate DNA ?
Evidence for a semi-conservative DNA replication
Summary
1
Xavier DANIEL, Ph.D.A
Goals of this lesson
The student can
Describe the semi-conservative DNA replication
Describe the evidence for the semi-conservative DNA replication
DNA Replication: Reminder !
Cell division requires replication of genetic material
Before (almost) each cell division, DNA is replicated
DNA replication occurs during the S phaseof the cell cycle
Each strand of the double-stranded DNA is used as a template
One double helix….. Two double helices
Each daughter cell owns - the same genetic material- the same genetic material as their parent cell
Xavier DANIEL, Ph.D.A
F: Genetic ControlDNA Replication is semi-conservative
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Xavier DANIEL, Ph.D.A
Goals of this lesson
Watson and Crick’s notice
Three ways to replicate DNA ?
Evidence for a semi-conservative DNA replication
Summary
Crick and Watson (1953)Nobel Prize Medicine1962
Xavier DANIEL, Ph.D.A
2 Watson and Crick’s notice
A / T
G / C
“It has not escaped our notice that the specific pairing we have
postulated immediately suggests a possible copying mechanism for the
genetic material”
Crick and Watson (1953)Nobel Prize Medicine1962
Xavier DANIEL, Ph.D.A
2 Watson and Crick’s notice
The semi-conservative modelAfter each replication, each double helix is made of
50% of old DNA 50% of new DNA
F: Genetic ControlDNA Replication is semi-conservative
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Xavier DANIEL, Ph.D.A
Goals of this lesson
Watson and Crick’s notice
Three ways to replicate DNA ?
Evidence for a semi-conservative DNA replication
Summary
Watson and Crick’s model = semiconservative replication
Two other models: the conservative model and the
dispersive model.
Xavier DANIEL, Ph.D.A
3 Three ways to replicate DNA ?
Old DNA
NewDNA
Conservative ?Dispersive ?Semi-conservative ?
Xavier DANIEL, Ph.D.A
3 Three ways to replicate DNA ?
Old DNA
NewDNA
Conservative ?Dispersive ?Semi-conservative ?
Xavier DANIEL, Ph.D.A
3 Three ways to replicate DNA ?
Old DNA
NewDNA
Conservative ?Dispersive ?Semi-conservative ?
Xavier DANIEL, Ph.D.A
3 Three ways to replicate DNA ?
Old DNA
NewDNA
F: Genetic ControlDNA Replication is semi-conservative
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Xavier DANIEL, Ph.D.A
Goals of this lesson
Watson and Crick’s notice
Three ways to replicate DNA ?
Evidence for a semi-conservative DNA replication
Summary
Which of the three models is right ?
Experiments in the late 1950s
Matthew Meselson and Franklin Stahl
Xavier DANIEL, Ph.D.A
Evidence for a semi-conservative DNA replication
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All DNA contains…15N ONLY
centrifugation
Xavier DANIEL, Ph.D.A
Evidence for a semi-conservative DNA replication
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Xavier DANIEL, Ph.D.A
Evidence for a semi-conservative DNA replication
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New DNA is lighter than old DNAOld DNA 15N
NewDNA 14N
Xavier DANIEL, Ph.D.A
Evidence for a semi-conservative DNA replication
4
New DNA is lighter than old DNAOld DNA 15N
NewDNA 14N
Xavier DANIEL, Ph.D.A
Evidence for a semi-conservative DNA replication
4
New DNA is lighter than old DNAOld DNA 15N
NewDNA 14N
Parent moleculedsDNA Parent molecule
ssDNAParent molecule
ssDNAParent molecule
ssDNAParent molecule
ssDNA
New nucleotides
Parent moleculessDNA
New strandssDNA
Parent moleculessDNA
New strandssDNADenaturation
Addition of
Xavier DANIEL, Ph.D.A
Evidence for a semi-conservative DNA replication
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F: Genetic ControlDNA Replication is semi-conservative
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5
Xavier DANIEL, Ph.D.A
Goals of this lesson
Watson and Crick’s notice
Three ways to replicate DNA ?
Evidence for a semi-conservative DNA replication
Summary
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