DNA & Protein SynthesisChapter 8

The Molecule of Heredity

Seeking the Genetic Material• 1928 Griffith finds that virulent bacteria

can transform nonvirulent bacteria into the deadly form. Virulent: able to cause disease

• 1944 Avery: found DNA was the molecule of heredity, not protein or RNA.

• 1952 Hershey and Chase: found that viruses injected DNA into host bacteria. DNA is confirmed as the unit of heredity.

Hershey and ChaseExperiment

Animation & Game

The Structure of DNA

• Structure was discovered by Watson and Crick in 1953, 1962 receive Nobel Prize.

• Double Helix: two strands twisted like a winding stair case.

• Made up of Nucleotides: Phosphate, Sugar (deoxyribose) and a Nitrogen base (A,T,C,G) (Pg. 185)

• Sugar and phosphate molecule are the same for each nucleotide. Nitrogen base changes.

Nitrogen Bases:• Adenine pairs with Thymine• Cytosine pairs with Guanine• Bases are held together by weak hydrogen

bonds.• A-T and C-G are called complementary base

pairs.• A mistake here is one form of Mutation.• Can you tell me the complementary strand

for : AATCGCGA? ______________

How did Watson and Crick find the structure?

• With help from fellow scientists such as…• Chargaff: 1949 discovered there are

always equal amounts of Adenine to Thymine and the same percentage of Cytosine to Guanine.

• Wilkins and Franklin: Photographed DNA with X-rays.(pg 187, Fig 10-4) Found helictical shape (i.e. Helix Shape).

Chargaff’s Ratios

Franklin Click:NOVA News Minute

DNA Replication Pg. 188

• DNA needs enzymes (protein) to copy or replicate itself.

• Double helix unwinds using DNA Helicase.

• DNA Helicase breaks the hydrogen bonds.

• Where the DNA breaks apart is called the replication fork. DNA polymerase (another enzyme) adds nucleotides at this point.

Replication

Movie

HHMI Replication

DNA

ReplicationHit Large MOV

Here is a great review of DNA and DNA Replication

• Please Activate this clip at home and go to the section you are interested in seeing.

The Review Button

Checking for errors

• DNA Polymerase also proof reads the strands

• A mistake in nucleotide pairing is a Mutation

• Multiple replication forks happen all at once so that the process is speedy.

DNA Review

Flashcards

What is RNA and how is it useful?

• RNA= Ribonucleic Acid

• Transcribes DNA and Translates it into proteins.

• Proteins are organic coupounds that have specific jobs in the cell. (Ex. Enzymes)

PBS Video

RNAi

What are the 3 types of RNA?• mRNA= Messenger RNA

– Transcribes or rewrites DNA’s message as mRNA, mRNA carries message to ribosome

• rRNA = Ribosomal RNA– Creates the ribosomes on the rough ER and

cytoplasm where proteins are made.

• tRNA = Transfer RNA– Transfers amino acids to the ribosomes and

translates the mRNA into protein. (Called Translation because the message changes from nucleic acid to protein, a different organic compound)

Transcription and TranslationCinema

• Don’t relax too much

• Pencils out? Notes ready? Lets work!

Transcription & Translation Movie

Highly detailedAnd very good

Overview Movie

Start Here

First Base

Second Base

Third Base

U C A G

  U    

UUUphenylalanine

UCUserine

UAUtyrosine

UGUcysteine

U

UUCphenylalanine

UCCserine

UACtyrosine

UGCcysteine

C

UUAleucine

UCAserine

UAAstop

UGAstop

A

UUGleucine

UCGserine

UAGstop

UGGtryptophan

G

  C    

CUUleucine

CCUproline

CAUhistidine

CGUarginine

U

CUCleucine

CCCproline

CAChistidine

CGCarginine

C

CUAleucine

CCAproline

CAAglutamine

CGAarginine

A

CUGleucine

CCGproline

CAGglutamine

CGGarginine

G

  A    

AUUisoleucine

ACUthreonine

AAUasparagine

AGUserine

U

AUCisoleucine

ACCthreonine

AACasparagine

AGCserine

C

AUAisoleucine

ACAthreonine

AAAlysine

AGAarginine

A

AUG (start)methionine

ACGthreonine

AAGlysine

AGGarginine

G

  G    

GUUvaline

GCUalanine

GAUaspartate

GGUglycine

U

GUCvaline

GCCalanine

GACaspartate

GGCglycine

C

GUAvaline

GCAalanine

GAAglutamate

GGAglycine

A

GUGvaline

GCGalanine

GAGglutamate

GGGglycine

G

The Lac Operon

• E. coli and the Lac Operon

• Only in Prokaryotes

• Fig 11-1, 11-2

The Lac Operon,

But Not the Operon that Lacks!

How do Eukaryotes control Gene expression?

• Transcription creates Pre-mRNA

• Pre-mRNA includes Introns and Exons

• Introns= Fillers

• Exons= Code for proteins

• mRNA is just the Exons

What do enhancers do?

• Enhancer’s causes the gene it is enhancing to be expressed. Transcription occurs in eukaryotes when an enhancer activates it.

Eukaryotic Transcription

Read and review 11-2

• Homeotic genes

• Homeobox

• Cancer, the types and causes

• The war on cancer

• Viruses and Cancer

• Oncogenes