DNA Structure and Replication 1

DNA Structure and Replication

Chapter 14 (Chromatin, oncogenes & TSG

in Chapter 10)

Topics you are not responsible for:Section 14.5: eukaryote replicationSection (p 268-269) on ‘replisomes’

End of Chapter questions:Understand: allApply: 1 – 6 & 8Synthesize: 1 & 3

Do all mQuiz questions

Do MolnQuiry Nucleic Acids Chapter

DNA Structure and Replication 2

History of the discovery of the genetic material - 1?

Bacteriophages infect Cells with DNA alone

Alfred Hershey Martha Chase experiments -- 1928

-- radiolabeled DNA and protein

HC-Experiment

DNA Structure and Replication 3

History of the discovery of the genetic material - 2?

P.A. Levene showed DNA isa polymer of nucleotides

Erwin Chargaff showed DNAcomposition differs among organisms

DNA Structure and Replication 4

What is the structure of a DNA strand?

Nucleotides

Phosphodiester linkages

Sugar-Phosphate Bone

3’ to 5’ orientation

DNA Structure and Replication 5

History of the discovery of the genetic material - 3?

J. Watson, F. Crick, R. Franklin and M. Wilkins

Determined the 3-D structure

What did Franklin and Wilkins contribute?

Crystalography

What did Watson and Crick Contribute?-- Double helix-- Antiparallel orientation-- Base pairing

DNA Structure and Replication 6

What is the structure of the DNA double helix?

Complimentary base pairing-- base pairs are hydrogen bonded

Antiparallel orientation

Major and minor grooves

Models

DNA Structure and Replication 7

How does DNA replicate -1?

Semiconservative replication

The M. Meselson and F Stahl experiment

MS-Experiment

DNA Structure and Replication 8

How does DNA replicate -2?

The need for RNA priming--”RNA Primase”

Adding nucleotides-- “DNA Polymerase”

5’ to 3’ orientation

Proofreading ability

NucleotidePolymerization

Proofreading

DNA Structure and Replication 9

How does DNA replicate -3?

Origins of Replication

Replication ‘forks’

HelicaseDNA gyrase

Replisomes

DNA Structure and Replication 10

How does DNA replicate - 4?

New strand 5 ‘ 3’ orientation

Leading & lagging strands

DNA HelicaseSS Binding proteinRNA PrimaseDNA Polymerase IIIDNA Polymerase ILigase

Time

DNA Replication

DNA Structure and Replication 11

What is the structure of eukaryotic chromatin?(from chapter 10; page 190)

Shape

Structure of chromatin

Nucleosomes

Functional areas

Centromeres

Telomeres

Replication

Supercoiling

Model

DNA Structure and Replication 12

Sickle-cell anemia mutation

What are mutations?-- see section chapter 20 section 20.2

Changes to the base sequence

Some examples

“Point Mutations”Base substitutionBase deletionBase chemical change

“Sequence mutations”DuplicationsDeletionsInversions

“Chromosomal aberrations”

DNA Structure and Replication 13

What types of chromosomal aberrations can occur?

DeletionsTranslocationsDuplications

-- aneuploidy-- polyploidy

Breakages

What is the role ofmutated tumor suppressor genes?

-- detection & repair of DNA-- cell cycle control-- triggering of apoptosis

Meningioma karyotypeLOH - #17

Aneuploidy - #s 9, 7, and 20Translocation/duplication - #s 2 and 6

DNA Structure and Replication 14

How is DNA damage repaired?

DNA polymerase “proofreading”

Mutation detection-- tumor suppressor genes

Excision repair (via endonuclease)

Other repair enzymesphotolyase thymine dimers

Excision Repair