The Genetic Code and
Translation
• Codon – three mRNA bases in a row that
code for an amino acid
Divide this mRNA strand into codons:
AUGGGCACUCUCGCAUGA
↓
AUG GGC ACU CUC GCA UGA
• Genetic Code – chart used to determine
which amino acid goes with a certain
codon
– Universal – all organisms use the same code
– There are 64 different codons, but only 20
amino acids. (So, there may be
more than one codon for an amino acid.)
– AUG codes for methionine (the “start” codon)
• Signals the beginning of protein production
– UAA, UAG, UGA – “stop” codons
• Signals the end of protein production (no amino
acid)
• Translation – mRNA is used to make a
protein
– Sequence of bases determine sequence of
amino acids
– Occurs at ribosomes
Steps of Translation
1. mRNA attaches to ribosome
2. tRNA brings amino acids to ribosome
-
tRNA anticodon is complentary to mRNA
codon
3. As ribosome slides down mRNA, more
amino acids are brought by tRNA.
4. Amino acids form peptide bonds and fold
to make the protein.
http://passel.unl.edu/pages/animation.php?a=translation.swf
DNA:
mRNA:
tRNA anticodons:
Amino acids:
TAC AGA CCC TTG CGG TCG ACT
Translation
Translation
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A = amino acid
B = tRNA
C = anticodon
D = codon
E = mRNA
F = ribosome
G = protein
Translation