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Amino acid

Amino acids are the basic constituents of proteins.

An amino acid is produced by the translation of an mRNA (transcribed from DNA).

DNA => mRNA => Amino acid => Proteins

The chain of amino acids forms the primary structure of proteins. Twenty standard amino acids are represented in the human genetic code. Of these, eight are essential (our body cannot synthesise them, it must get them from our food): leucine, tryptophan, lysine, methionine, phenylalanine, threonine, valine, isoleucine.

Histidine and arginine are semi-essential. Only newborns need to get these from their food.

Cysteine, glycine and tyrosine may be essential for certain populations. For example, a patient with phenylketonuria cannot have a high phenylalanine intake. But phenylalanine is needed for the synthesis of tyrosine, so this then becomes an essential amino acid and must be acquired from food. The term protein is used for chains of more than 100 amino acids. If there are fewer, the terms polypeptide (20-100 amino acids) or peptide (less than 20) are used.


An allele is a version of a gene. Every human being has two alleles per gene (one from the mother and one from the father).


ATP = Adenosine Triphosphate

ATP is a molecule needed to provide the energy for chemical reactions in the body.

Autosomal recessive disease

An autosomal recessive disease is a disease that originates from both the father and the mother.

For the child to be ill, both the father and the mother must pass on the mutated allele. If only one of them passes on the mutated allele, the child will not have the disease.