School Science Lessons
Genetic code
2012-05-12 SPwp
Please send comments to: J.Elfick@uq.edu.au

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The code for a amino acid is a 3 letter codon. Most amino acids have more than one codon,
e.g. phenylalanine has TTT and TTC. End of chain has 3 codons. The first letter in a codon is in
position 1, the second in position 2 and the third in position 3. After position 3 is END of chain.
Code Nucleic acid
T Thymine (for DNA, U Uracil for RNA) (Thymine is 5-methyl uracil.)
C Cytosine
A Adenine
G Guanine

.	Position 2	Position 2	Position 2	Position 2	.
Position 1	T	C	A	G	Position 3
T	Phenylalanine	Serine	Tyrosine	Cysteine	T
T	Phenylalanine	Serine	Tyrosine	Cysteine	C
T	Leucine	Serine	END	END	A
T	Leucine	Serine	END	Tryptophan	G
C	Leucine	Proline	Histidine	Arginine	T
C	Leucine	Proline	Histidine	Arginine	C
C	Leucine	Proline	Glutamine	Arginine	A
C	Leucine	Proline	Glutamine	Arginine	G
A	Isoleucine	Threonine	Asparagine	Serine	T
A	Isoleucine	Threonine	Asparagine	Serine	C
A	Isoleucine	Threonine	Lysine	Arginine	A
A	Methionine	Threonine	Lysine	Argining	G
G	Valine	Alanine	Aspartic acid	Glycine	T
G	Valine	Alanine	Aspartic acid	Glycine	C
G	Valine	Alanine	Glutamic acid	Glycine	A
G	Valine	Alanine	Glutamic acid	Glycine	G

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Amino acids and their 64 codons
Ala Alanine GCT, GCC, GCA, GCG
Arg Arginine CGT, CGC, CGA, CGG, AGA, AGG
Asn Asparagine AAT, AAG
Asp Aspartic acid GAT, GAC
Cys Cysteine TGT, TGC
Gin Glutamine CAA, CAG
Glu Glutamic acid GAA, GAG
Gly Glycine GGT, GGC, GGA, GGG
His Histidine CAT, CAT
Ile Isoleucine ATT, ATC, ATA
Leu Leucine TTA, TTG, CTT, CTC, CTA, CTG
Lys Lysine AAA, AAG
Met Methionine ATG
Phe Phenylalanine TTT, TTC
Pro Proline CCT, CCC, CCA, CCG
Ser Serine TCT, TCC, TCA, TCG
Thr Threonine ACT, ACC, ACA, ACG
Trp Tryptophan TGG
Tyr Tyrosine TAT, TAC
Val Valine GUU, GUC, GUA, GUG
END of chain TAA, TAG, TGA
Position 1 is called the 5' end
Position 3 is called the 3' end.

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