Protein Synthesis

• Transcription

• Translation

http://www-class.unl.edu/biochem/gp2/m_biology/animation/gene/gene_a1.html

Animation – overview of transcription/translation

http://www-class.unl.edu/biochem/gp2/m_biology/animation/gene/gene_a2.htmlTranscription - detail

http://www-class.unl.edu/biochem/gp2/m_biology/animation/gene/gene_a3.htmlTranslation - detail

Types of RNA

• mRNA

• tRNA

• rRNA

3 steps of transcription•Promoter Region

•RNA Polymerase

•Primary Transcript is made from the coding strand of DNA

•Terminator Region

Transcription Animation

RNA Processing

mRNA has a short life span

•A cap is added

•A poly-A tail is added

Protect enzymes from breaking down mRNA in the cytoplasm

•Introns

•Exons

Splicing is the process of removing introns and rejoining cut ends

The Genetic Code (pg 237)

Combine DNA nucleotides to code 20 different “words” (amino acids)

The Genetic Code

Translation

http://www-class.unl.edu/biochem/gp2/m_biology/animation/gene/gene_a3.htmlTranslation Animation – detailed:

Making a Protein

1. DNA serves as a template in for making RNA in the nucleus

2. RNA goes to the cytoplasm

3. RNA attaches to the ribosome

4. tRNA contains an anticodon that is complementary to the codon of the mRNA

5. Amino acids are bonded together to make a polypeptide

THEDOGBITTHECATTHEDOGBITTHECAR

POINT MUTATION:

A change in a single base pair in DNA

THE DOG BIT THE CATTHE DOG BIT THE CAR

Genetic Mutations

Genetic Mutations

THEDOGBITTHECATTHE DOB ITT HEC AT

If a single base is added or deleted from DNA, this is a FRAMESHIFT MUTATION, because it shifts the reading of codons by one base.

A different sequence of codons and amino acids results.

Genetic Mutations

Genetic Mutations

DNA BASE SEQUENCES:

Normal Hemoglobin GGG CTT CTT TTT

Sickled Hemoglobin GGG CAT CTT TTT

(Sickle-cell anemia)Point Mutation or Frameshift Mutation?

Sickle Cell Anemia

POINT MUTATION OR FRAMESHIFT MUTATION?

The 20 Amino AcidsGeneral Structure

(Variable or R group)

CODON

BINGO!

VIRUSES

• Living or Not?• No cells• Tiny particles• Replicate• Evolve• Do not carry out own

metabolism• Do not respond to

environment• Different structures

http://www.newtown.k12.ct.us/~royalk/viruses.htm

How do viruses replicate?

• Host cell enzymes replicate viral DNA

• Viral genes transcribed and translated on host ribosomes

• Proteins reassemble into virus particles

• The cells lyses (splits)when there are many viruses in the host cell; they infect other cells

Lytic Infections Lysogenic Infections

• Viral DNA inserts into cellular DNA• Viral DNA is therefore copied when

the host cell replicates• No production of new viruses• Stress to host can activate cell to

enter into lytic cyle (example: starvation)

Protein structure• Primary• Secondary• Tertiary• Quaternary

Chromosome Structure

DNA helix

nucleosomes

30 nm solenoid

30 nm solenoid

chromatin loops

scaffold-associated condensed loops

Chromatin

30 nm solenoid

chromatin loops

scaffold-associated condensed loops

metaphase chromosome

scaffold-associated condensed loops

How nucleosomes affect transcription

DNA wrapped around

histone proteinstwo H2Atwo H2Btwo H3two H4

nucleosome particle in a 30nm fiber

histone octamer

How nucleosomes affect transcription

• (+)-charged lysines of histone proteins interact with (-)-charged phosphates of DNA

+

+

+

+

• histone acetylation is correlated with transcriptional activity

• reversible acetylation of lysines neutralizes charges

• DNA decondenses from histone octamer

• DNA is tightly wrapped around histone octamer

Ac

Ac Ac

Ac

+

N-O-C-CH3

O||

|H

lysine

acetylated lysine

Transcription activators can promote histone acetylation

TATAHRE

nuclear hormone receptors

TATA

co-Activator(s)

coA HAT

Histone Acetyl Transferase

TFIID

histone acetylation

                                            

Copyright © The National Human Genome Research Institute