Protein Synthesis
Translation
The Big Picture
• DNA (genes)
information copied
to make 
• mRNA
(transcription)
• Information in
mRNA sequence
used to put
together 
• Chain of amino
acids(protein)
• Proteins determine
physical traits of
organism
Translation: Why
• mRNA has copied information from DNA into
“nucleic acid” language (A,U,G,C)
• Must be translated into “protein” language
(amino acids)
Translation
Building Blocks of Proteins
• Proteins are made of
subunits called amino
acids
• These subunits are
comprised of :
– Amino group
– Carboxyl group
– R group is different for
each amino acid
Translation
Building Blocks of Proteins
• 20 different amino acids make up all proteins
• Order of amino acids gives protein specific
characteristics
Amino acids:
Building Blocks of Proteins
Peptide bond joins
amino acids in proteins
Translation: The Code
• 4 letters in RNA:
A, U, C, G
• 3 letters = code for
each amino acid
• Codon = 3 base code
for a specific amino
acid
Translation: The Code
• 64 possible
combinations (4x4x4)
• More than 1 code for
some amino acids
• Start = AUG
• Stop = UAA, UAG, UGA
Translation: Where
• Cytoplasm of cell
Translation: The Players
• mRNA with 3-base codons
• Start codon
• Stop codon
Translation: The Players
• tRNA
• Matches correct amino
acid with codon
• Anticodon
• Amino acid
Translation: The Players
• Composed of
rRNA & protein
• Ribosomes
assemble the
protein
• Move along
mRNA
• tRNA brings
amino acids
Translation: Initiation
• Begin at start codon
• Assemble ribosomes
• http://www.phschool.com/science/biology_pl
ace/biocoach/translation/init.html
Translation: Elongation
• tRNA matches anticodon with codon in mRNA
to bring correct amino acids to protein
• Peptide bonds are formed between amino
acids
• http://www.phschool.com/science/biology_pl
ace/biocoach/translation/elong1.html
Translation: Termination
•
•
•
•
“Stop” codon is reached
Protein is released from ribosome
Protein folds into 3-D shape
http://www.phschool.com/science/biology_pl
ace/biocoach/translation/term.html
Translation
• Many proteins can be translated from
a single message
The Complete Process
• http://www.wisconline.com/objects/index_tj.asp?objid=AP1302
Transcribe & translate a gene
• Practice!
• http://gslc.genetics.utah.edu/units/basics/tra
nscribe/