Protein Synthesis

Protein SynthesisProtein Synthesis

DNA

mRNA

Transcription

Cell

Protein (chain of Amino acids)

TranslationRibosome

DNA and Protein SynthesisDNA and Protein Synthesis

•DNA contains the genetic information or genes to make proteins

• Proteins are chains of amino acids linked together

• These proteins determine the physical traits of an organism and control cellular functions.

What is a Gene?• A genegene is a certain length or piece of

DNA on a chromosome

• A gene is made of 2 parts:

1. Exon – the expressed parts of the DNA sequence or part that is used to make a protein

2. Intron – the intervening, “junk DNA”, not expressed or used

• Parts are cut, put together and then used to make RNA and proteins

How to make a Protein…How to make a Protein…

• Step 1: Use DNA to make a messenger RNA molecule - TranscriptionTranscription

• Step 2: Decode that messenger RNA to see which amino acids are needed to make a protein – Translation

Flow of Information:Flow of Information:DNA DNA RNANA Proteins Proteins

Protein SynthesisProtein Synthesis

Step 1: Step 1: TranscriptionTranscription

1.1. DNA unzips DNA unzips

2. Messenger RNA (or mRNA) mRNA) is made from DNA using base pairs

RNA is different from DNA:

a) RNA is single stranded, not double stranded

b) Instead of deoxyribose, it has ribose

c) instead of Thymine, it uses Uracil

3) mRNA carries the genetic code from the nucleus to the ribosome in the cytoplasm

Protein Synthesis: Transcription

DNA

Cytoplasm

Nucleus

Eukaryotic Transcription

ExportG AAAAAA

RNA

Transcription

Nuclear pores

G AAAAAA

RNAProcessing

mRNA

CodonsCodons CodonCodon: is a group of three bases that code for a specific

amino acidamino acidex: AAA = Lysine

The codons code for 20 amino acids

o Just like the alphabet has 26 letters to make all the words we know, the 20 amino acids make all the different proteins found in living organisms

The codons are the template for protein synthesis, which takes place on the ribosomes (rRNA)ribosomes (rRNA) in the cytoplasmcytoplasm

DNA and Protein Synthesis – Codons and amino DNA and Protein Synthesis – Codons and amino acidsacids

Name the Amino Acid:

UAU

CCG

AGU

GCA

Tyrosine

Proline

Serine

Alanine

Translation:

1. In the cytoplasm, mRNA attaches to the rRNA (ribosomal RNA) and starts reading the codons

2. tRNA (transfer RNA) – carries amino acids to the ribosome and attaches them together to make a growing protein chain

3. When protein production is complete, the ribosome releases the protein chain, and the protein folds into a 3D shape

Protein Synthesis: TranslationProtein Synthesis: Translation

Protein Synthesis: Translation

AE

Large subunit

P

Small subunit

Translation - Initiation

fMet

UACGAG...CU-AUG--UUC--CUU--AGU--GGU--AGA--GCU--GUA--UGA-AT GCA...TAAAAAA5’mRNA

3’

AE

Ribosome P UCU

Arg

Aminoacyl tRNA

PheLeu

Met

SerGly

Polypeptide

CCA

Translation - Elongation

GAG...CU-AUG--UUC--CUU--AGU--GGU--AGA--GCU--GUA--UGA-AT GCA...TAAAAAA5’mRNA

3’

AE

Ribosome P

PheLeu

Met

SerGly

Polypeptide

Arg

Aminoacyl tRNA

UCUCCA

Translation - Elongation

GAG...CU-AUG--UUC--CUU--AGU--GGU--AGA--GCU--GUA--UGA-AT GCA...TAAAAAA5’mRNA

3’

AE

Ribosome P

CCA

Arg

UCU

PheLeu

Met

SerGly

Polypeptide

Translation - Elongation

GAG...CU-AUG--UUC--CUU--AGU--GGU--AGA--GCU--GUA--UGA-AT GCA...TAAAAAA5’mRNA

3’

AE

Ribosome P

Translation - Elongation

Aminoacyl tRNA

CGA

Ala

CCA

Arg

UCU

PheLeu

Met

SerGly

Polypeptide

GAG...CU-AUG--UUC--CUU--AGU--GGU--AGA--GCU--GUA--UGA-AT GCA...TAAAAAA5’mRNA

3’

AE

Ribosome P

Translation - Elongation

CCA

Arg

UCU

PheLeu

Met

SerGly

Polypeptide

CGA

Ala

GAG...CU-AUG--UUC--CUU--AGU--GGU--AGA--GCU--GUA--UGA-AT GCA...TAAAAAA5’mRNA

3’