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Dolan DNA Learning Center: DNA Timeline

http://www.dnai.org/timeline/index.html

Online materials: History of DNA

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Questions about Inheritance

What molecule is responsible?

How is information encoded?

How does the molecule replicate?

How does the molecule change?

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Chromosomes

Proteins

Nucleic Acid

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Nuclein

Friedrich Miescher, Switzerland &

Germany

1871- Described isolation of nucleinfrom nuclei (from human pus!)

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DNA

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DNA

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DNA

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DNA

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Protein or Nucleic Acid?

Phoebus Levene

Tetranucleotide theory

Protein initially favored

More letters

More complex

structure

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Transformation

R transformedto S

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Transformation

Avery, MacLeod & McCarty, 1944

Isolation of the transformation factor

S strain

DNaseProtease

RNase

S strain

DNA

R strain

R strainTransformed

to S

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Hershey-Chase Experiment

Bacteriophage

Composed of protein & DNA

Martha Chase & Alfred Hershey

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Hershey-Chase Experiment

What do phage inject into bacteria?

Radioisotope Tracers

35S- labels proteins

32P- labels DNA

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Hershey-Chase Experiment

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Erwin Chargaff

Biochemist

Precise quantification of

DNA nitrogenous basesin various organisms

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Erwin Chargaffs data

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Chargaffs Rules

For all species:

[Adenine] [Thymine]

[Guanine] [Cytosine]

For each species:

[Adenine]:[Guanine] is distinct

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Rosalind Franklin

X-ray diffraction

X-Ray

Generator

D

N

A

X-Ray Film

DNA is a helix of two strands

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Watson & Crick

Chargaffs Rules

Franklins diffraction

data Components of DNA:

Francis Crick & James Watson

CytosineThymine Adenine GuaninePhosphate Deoxyribose

Pyrimidines Purines

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Aligning Bases in the DNA Model

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Aligning Bases in the DNA Model

Hydrogen

Bonding

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Models of DNA Replication

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Messelson & Stahl

Experiment

Martha Chase is unidentified person

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Messelson & Stahl Experiment

14N 15N

Centrifugation

DNA DNA

Densit

yGradient

DensityGradient

E. coli culture E. coli culture

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Messelson & Stahl Experiment

1stReplication

after switch

2nd Replication

after switch

Before

switch

15N

14N

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Does Conservative Model Fit?

1stReplication

after switch

2nd Replication

after switch

Before

switch

15N

14N

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Does Dispersive Model Fit?

1stReplication

after switch

2nd Replication

after switch

Before

switch

15N

14N

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Does Semi-conservative Model Fit?

1stReplication

after switch

2nd Replication

after switch

Before

switch

15N

14N

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DNA Replication in Bacteria

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DNA Replication in Eukaryotes

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DNA Polymerase

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Getting Started: RNA Primer

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Leading & Lagging Strands

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Bioflix DNA Replication Movie

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Telomers

Telomerase

TTAGGG

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Chromatin- Packaged DNA

DNA double helix(2 nm in diameter)

DNA, the double helix

Nucleosome(10 nm in diameter)

Histones

Histones

Histonetail

H1

Nucleosomes, or beads ona string (10-nm fiber)

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30-nm fiber

30-nm fiber

Loops Scaffold

300-nm fiber

Chromatid(700 nm)

Replicatedchromosome(1,400 nm)

Looped domains(300-nm fiber) Metaphase

chromosome

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5m