Protein Synthesis

The Molecule of Life:Transcription and Translation

Transcription and Translation

Transcription begins the process of protein synthesis

Translation results in the end protein molecule

Several organelles in the cell are involved

Cell Organelles Involved in Protein Synthesis (186)

Transcription: Start of Protein Synthesis Where?

Nucleus in Eukaryotes Cytoplasm in Prokaryotes

What? Many cell organelles involved RNA Polymerase plus some minor proteins DNA code becomes encoded in mRNA

Transcription: Start of Protein Synthesis When?

When RNA is needed

Why? RNA’s serve many important functions in

cells RNA encodes protein sequences

How?

Transcription Defined

Transcription: to transfer a code into another code ie. To rewrite one language into another

http://blog.coturnix.org/2008/05/01/lithium_circadian_clocks_and_b_2/

Where are we?

Transcription

How? mRNA made 5’3’ directionality DNA unzips only at a specific gene

sequence for a specific protein Usually only one strand of DNA is read to

form a complementary copy of the mRNA

Transcription

Uses Base-pairing but U instead of T pairs with A.

RNA nucleotides “float” into place with the aid of RNA polymerase and complementary base pairing occurs

There are nonsense codes at the end of the gene that terminate mRNA synthesis.

mRNA breaks off and moves out of the nucleus into the ribosomes of the cytoplasm

Same idea as with DNA replication Transcription Animation Transcription & translation - fast

Transcription: Layout

5’ end RNA

3’end RNA

mRNA Enters Cytoplasm

http://www.dnatutorial.com/RNATranscriptionAnimation.shtml

Translation

What? mRNA Protein molecule

Where? Cytoplasm Ribosomes are main organelles

Translation

When? When proteins are need, after mRNA is made

Why? Proteins are vital for cells

Enzymes, tissues, hormones, cell structure all require proteins

The Genetic Code

Translation: Defined

Translation: to interpret a code into meaning.

In biology: The process by which messenger RNA directs the amino acid sequence of a growing polypeptide during protein synthesis.

Proteins: Structure and Function Amino acids connect to form small

chains called peptides, which get larger and form polypeptides.

There are 20 amino acids useful to humans

We consume these in our diet, our body makes a few

Proteins: Structure and Function In anabolism, our body needs to

assemble these amino acids into specific protein structures. A missing amino acid means an entire protein cannot be made—the RNA cannot “fill” the hole left by its absence

A.A. allow the protein molecule to form its necessary structure

Proteins have many structures/shapes

Peptide Bond Formation: Dehydration Synthesis

From Amino Acid to Protein Structure

The Big Question?

How do amino acids assemble themselves correctly?

Translation

How? Ribosomal Subunits

Small subunit Large subunit

Codon on mRNA Triplet nucleotide code used Each triplet codes for a specific tRNA

attached to a specific amino acid

Translation

How? mRNA, tRNA, & rRNA are all used

A couple definitions

CODON: a triplet of nucleotides on the mRNA Triplet codes for a specific tRNA

complementarity The codon is the genetic code

ANTICODON: A triplet of nucleotides on the bottom of the

tRNA Triplet anticodon complements the mRNA

codon Brings attached to its 3’ end an amino acid

The Genetic Code

Test for Understanding the code A DNA sequence has the

following bases: T A C - A G A - T T A - G G G - A T T What amino acids does it code for? (You'll need to use the codon chart)

mRNA CODONSAUG UCU AAU CCC UAAMet–ser – asn – pro-stop

AUG usually is “START”UAA is “STOP”

Amino acid sequence is actually SER-ASN-PRO

tRNA each has one specific amino acid and this is how amino acids “know” the sequence of attachment !

Recall tRNA

Anticodon attaches to codon

Amino acid valine is attached to this specific tRNA

Valine will always attach to tRNA with the same anticodon

Amino acid binding site is amino acid specific

Summary

Translation DNA Rap

http://www.biologycorner.com/bio4/notes/gene-expression.php

Why is this important?

Genetic Engineering Gene Splicing

Mutations Cloning http://www.johnkyrk.com/DNAtranscription.html Castle Analogy