Protein Synthesis
Part II: Translation
Biology
Translation Overview
p  mRNA
is decoded into a polypeptide chain
p  tRNA uses mRNA to synthesizes a protein
mRNA
p  Codon
mRNA
– three consecutive bases on
tRNA
p  Anti-codon
–
three bases on
tRNA that are
complimentary
to the mRNA
codon
p  Carries one kind
of amino acid
Translation – 10 Steps
1. 
2. 
mRNA leaves the
nucleus, attaches
to a ribosome in
the cytoplasm
ribosome finds
the start codon
(AUG)
3. 
tRNA with the anticodon (complimentary
to the mRNA start
codon) brings in the
first amino acid
4. 
The ribosome moves
down the mRNA to the
next codon; tRNA
brings in the next
amino acid
5. 
6. 
7. 
8. 
Peptide bond forms
between the two amino
acids.
Ribosome releases the
tRNA from the mRNA
The tRNA moves away
from the ribosome, leaving
the amino acid behind.
The next tRNA enters and
binds to the next codon on
the mRNA
9. 
10. 
Adding of amino acids and releasing of
tRNA continues; this forms a polypeptide
chain.
Translation ends ends the ribosome
reaches a stop codon.
***A new polypeptide chain is now
complete!
It will then be folded to make a protein.
How do you know what amino acid to
use?
p mRNA
codon is
used in a
decoder chart
to determine
the correct
amino acid
p (pg 32)
Decoder Chart #1 –
How do determine what amino acid goes with the mRNA s codon
CODON = AUG
Start in the center and work
your way out
A
U
G
Amino acid is methionine
Try finding the amino acid for the codon CUA
LEUCINE