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amino acid

Amino acids are the building blocks of proteins. Put very simplistically, our genes tell our bodies which amino acids to put into the proteins that we make, and it is the proteins that make up the significant constituents of our bodies. Myelin Basic Protein (MBP) is an example of one such protein.

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
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
Symbols Used for Nucleotide and Amino Acid Sequence Data

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