Protein Synthesis

From DNA to protein

And viruses

BIG PICTURE

• Processing of Gene Information - Prokaryotes versus Eukaryotes

• Transcription and Translation

Beadle and Tatum

George Beadle and Edward Tatum during the late 1930s

and early 1940s

• Using Neurospora crassa bread mold determined "one gene one enzyme hypothesis"

•has since been modified to "one gene one polypeptide"

Protein Synthesis Overview

Learn these Terms

• Transcription = DNA → mRNA

• Translation = mRNA → protein

Three Bases Lingo

• DNA Triplet ATC

• mRNA Codon UAG

tRNA Anti-codon AUC

Three Bases Lingo

• DNA original template

• mRNA codes from DNA, takes to cytoplasm

tRNA brings amino acid to ribosomes

rRNA structure of ribosome

Transcription

• DNA never leaves the nucleus

• It codes to mRNA to take the message outside the nucleus

• What do you see?

• Transcription Animation (HOT!!)

Protein Synthesis Animation

TeacherTube Videos –Protein Synthesis (good and to the point)

TeacherTube Videos - DNA to Protein

Introns and Exons

• Primary mRNA = exons + introns

• INTRONS (noncoding region of mRNA) are discarded

• The coding regions, spliced together RNA are called EXONS. = Mature mRNA

SPLICING ANIMATION

• Spicing Animation from NobelPrize.org Click on: Schematic animationof mutually exclusive exons»

• Before the mRNA leaves the nucleus, the introns are removed, and the exons are spliced together.

• How Spliceosomes Process RNA

Intron and Exon Summary

TRANSLATION

• mRNA (genetic language) needs to be translated into protein language

• VCAC: Molecular Processes: Translation: The Movie

TRANSLATION

• Coding from mRNA to making protein

• Animations (click here for translation animation)

• Transcribe and Translate a Gene (good activity)

The mRNA travels out of the nucleus through nuclear pores to a ribosome in

the cytoplasm

The mRNA The mRNA binds to a binds to a ribosome ribosome Ribosome Ribosome translates translates codons (use codons (use chartchart))

Translation

•Ribosome “reads” each codon (3 bases) on the mRNA.

• The mRNA “chart” is consulted and the correct amino acid is determined.

•What amino acids are being requested?

ANSWER

AGC =cysteine

UGA =STOP

CCU=proline

AGC =serine

GGA=glycine

CAA=glutamine

tRNA

• transports amino acids to ribosomes

• There is a specific amino acid for each tRNA

Job of tRNA

• Complements the codon of mRNA and picks up the appropriate amino acid ANIMATION:

Animation of Translation

•A tRNA with the anticodon complementary to the codon is sent to pick up the requested amino acid and bring it to the ribosome.

tRNA’s hang out in the cytoplasm. Think of them as trucks that transport amino acids from where they float around in the cytoplasm, to the ribosome. Think of the anticodon as the license plate on the tRNAthat matches the mRNA codon.

APE slots on the ribosome

• The ribosome attaches to the mRNA and provides a slot (A) for the tRNA to slide into so it can match the mRNA.

Note the P and A site

• Protein Synthesis: Translation

• A site – Amino acid is dropped off

• P site – Polypeptide builds

• E site-polypeptide exits

There are 20 Amino Acids

• These 20 are shared by all living organisms

Notice AUG codon means “start” building a new protein. UAA,

UAG, UGA mean “stop’ building the protein.

All mRNA’s start with AUG, so all DNA genes start with______?

Answer

•Methionine

Nice Animations of Protein Synthesis

• Shows Nucleus to Protein

• ☺Protein Synthesis Animation

Prot PPt s s Pei he i L r ea i g P t v tP P c i il s Pl P r PstPF a h aea

ll t oa i

• THINK:

• What would happen if something caused the base sequence to change?

• What sorts of things could cause this?• Could the base changes be repaired?• Would those changes be passed on to

the individual’s offspring?

MUTATION:

A change in the base sequence of a gene resulting in a different base sequence and thus different amino acid sequence.

What causes mutations? MUTAGENS

Examples of mutagens?

Thalidomide baby…

GOOD OR BAD?

Mutagen =any source of mutation is a physical or

chemical agent–EX: X-rays–UV light–cigarette components–Hazardous chemicals

Mutation Lingo

• Mutation = any change in the genetic material (nucleotide sequence of DNA)

Gene (point)mutations

SUBSTITUTION – Replace one base for another. Minimal effect

ADDITION – Adding a base

DELETION – removing a base

•Frameshift mutations =change every amino acid that follows the point of mutation

Chromosome Mutations

Translocation•

• Inversion• Segment of a

same chromosome is turned end to end

has moved one segment of a chromosome to a different chromosome

Frameshift

• Animation Quiz 5 - Addition and Deletion Mutations

Translocation

Mutation Animations

• What change do you notice?

Translocation 9 and 22

Name the mutation

• Animation Quiz 1

• (Not for the faint of heart) Human Mutants: Mutant Human Organs : Video : Discovery Channel Channel

Also could have substitution

Cystic Fibrosis Deletion

Albinism is due to a mutation of the melanin pigment gene. A one base substitution results in only 1 amino acid being in error.

ALBINISM

AAGGTTCGGAGT (DNA)

type of mutation Amino acids

AACGTTCGGAGT:____________________

AAGGTCTCGGAGT:____________________

AAGGTTCGAGT:_______________________

AAGGTTCGGAGT (DNA)

type of mutation Amino acids

AACGTTCGGAGT:____________________Substitution (C for the G)

AAGGTCTCGGAGT:____________________Insertion (the C)

AAGGTTCGAGT:_______________________Deletion (the G)

Chromosomal mutations

Affect the entire chromosome - often fatal.

Mutagens can cut up DNA into pieces.

When Repair mechanism reassembles them, they may be in the wrong order.

Oncogenes

Genes that when mutated result in cancer.

EXAMPLE: BRCA1 and BRCA2

Found to cause breast cancer on 81-kb region of human chromosome 17

NEWS FLASH!!!!

• Not every gene in your body is translated into polypeptides all the time.

OPERON

• A cluster of genes under the control of a promoter (beginning of gene)

Promoter

• a nucleotide sequence that enables a gene to be transcribed

Operator

• a segment of DNA that a repressor or activator binds to

Lac Operon (promoter and repressor)

• Animation Quiz - The Tryptophan Repressor

LAC OPERON (start making lactase)

• The lac Operon ANIMATION

• (If lactose is present, the repressor attaches to it. The genes to break down the lactose (lactase) can be made.)

• PICK ME VCAC: Molecular Processes: Lac Operon: The Movie

HOX Genes

• Hox genes are defined by a DNA sequence known as the homeobox, which is a sequence of 180 nucleotides

HOX GENES

• “Body Plan Genes”

HOX GENES: TELL THE BODY WHERE TO PUT THE PARTS

Viral Infections

Viruses

• Nothing more than packaged genes

• Simple tools for geneticists

• HIV EBOLA

Bacteriophage Infection (SEM)

Bacteriohage Infection

Every virus has two stages

• a dormant, particulate, transmissible stage called the virion stage

• an active, intracellular stage called the infectious stage

Infectious Stage: Lytic Infection

1.attachment

2. Insertion of virus DNA

3. replication of virus components

4.packaging and assembly of new virions

5. exit from cell –”lysis” bursts

Bacteriophage enzyme lyses thebacterium’s cell wall, releasingnew bacteriophage particles thatcan attack other cells.

Bacteriophage proteins and nucleic acids assemble into complete bacteriophage particles

Bacteriophage takes over bacterium’s metabolism, causing synthesis of new bacteriophage proteins and nucleic acids

Bacteriophage injects DNA into bacterium

Bacteriophage attaches to bacterium’s cell wall

Bacteriophage

Bacteriophage DNA

Bacteriophage protein

Bacteriophage protein coat

Bacteriophage DNA

Bacterialchromosome

Lytic Cycle

The Lytic Cycle

Go to Section:

LYTIC INFECTION

• Lytic Infection Animation

Lysogenic Infection

• The viral DNA becomes integrated into the bacterial DNA after infection. It is replicated along with the host DNA when the host reproduces. The viral DNA is referred to as a prophage.

Bacteriophage proteins and nucleic acids assemble into complete bacteriophage particles

Bacteriophage enzyme lyses the bacterium’s cell wall, releasing new bacteriophage particles that can attack other cells

Bacteriophage DNA inserts itself into bacterial chromosome

Bacteriophage DNA (prophage) may replicate with bacterium for many generations

Bacteriophage DNA (prophage) can exit the bacterial chromosome

Bacteriophage DNA forms a circle

Bacteriophage DNA

Bacterialchromosome

Bacteriophage injects DNA into bacterium

Prophage

Lytic Cycle

Lysogenic Cycle

A Lysogenic Infection

Go to Section:

DIAGRAM COMPARISON

• Lytic and Lysogenic Infections

Virus Examples

• RNA instead of DNA: cold, flu, HIV, polio, measles, mumps

• DNA viruses: herpes. Chicken pox, hepatitis

• Herpes infections may flare up when under stress, a cold, or sunburn

Ebola Virus

• Causes hemorrhagic fever

• Movie Outbreak

Hanta Virus

• Southwestern US mice carried it

cardiovascular collapse, respiratory failure, and death

HIV

• Has 2 copies of RNA

• Is a retrovirus (RNA to DNA)

• Carry enzyme reverse transcriptase

Aids infected cells

• HIV = Human Immunodeficiency Virus

• AIDS = Acquired Immune Deficiency Syndrome