In order to understand how amino acids are glued together to make proteins, we must look at the DNA (deoxyribonucleic acid) that is present in almost all the cells in our bodies.

DNA is built up of very many sub-units called neucleotides, each of which contains a chemical "base". There are only four different bases and thus only four different nucleotides. The four bases are adenine (A), thymine (T), cytosine (C) and guanine (G).

Genes are sections of DNA, in which the neucleotides are viewed in groups of three called "triplets" or "codons". Each codon "codes" for a particular amino acid. A gene is terminated by a stop code or terminator which is represented by one of three codons that do not code for amino acids.

There are 20 different amino acids that are used in animals (there are others that are used in plants). There are 64 different codons and most of the 20 amino acids are coded for by more than one triplet (see table below).

The process of synthesing amino acids from genes is known as transcription. During transcription, a gene is echoed from the DNA into a complementary form called ribonucleic acid (RNA).

From the RNA, amino acids are produced and are joined with one another with a peptide bond. The resulting sequence of amino acids is known as peptide string or polypeptide. Proteins are derived from these polypeptides.
 
 

The 20 Amino Acids and the stop code (Terminator)

Abbreviation	Amino acid name	Neucleotide sequences (codons)
Ala	Alanine	GCT, GCC, GCA, GCG
Arg	Arginine	CGT, CGC, CGA, CGG, AGA, AGG
Asn	Asparagine	AAT, AAC
Asp	Aspartic Acid	GAT, GAC
Cys	Cysteine	TGT, TGC
Gln	Glutamine	CAA, CAG
Glu	Glutamic Acid	GAA, GAG
Gly	Glycine	GGT, GGC, GGA, GGG
His	Histidine	CAT, CAC
Ile	Isoleucine	ATT, ATC, ATA
Leu	Leucine	TTG, TTA, 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, AGT, AGC
Thr	Threonine	ACT, ACC, ACA, ACG
Trp	Tryptophan	TGG
Tyr	Tyrosine	TAT, TAC
Val	Valine	GTT, GTC, GTA, GTG
End	Terminator	TAA, TAG, TGA

You will sometimes see these abbreviations:
Asx               Aspartic Acid or Asparagine      GAT,GAC,AAT,AAC
Glx               Glutamic Acid or Glutamine      GAA,GAG,CAA,CAG
Xxx or Xaa    Unknown
where the derivation is uncertain or unknown.

Amino Acid links:
Encyclopedia Entry - amino acid
Encyclopedia Entry - peptide
Encyclopedia Entry - protein
Encyclopedia Entry - nucleic acid
Incomplete nucleic acid sequences
DNA_and_amino_acids_nomenclature
Symbols Used for Nucleotide and Amino Acid Sequence Data

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