Genetic disorders

Genetic disorders are diseases of anatomical or physiological function caused by inherent or sporadic mutations in the DNA sequence of one or more genes. The disease can be either familial, ie. inherited from one or both parents, or sporadic, ie. a random mutation based upon environmental factors. (NB: some genetic diseases can be either of these, for example familial or sporadic retinoblastoma.)

DNA mutations can manifest in a number of different ways, such as:

Deletions: eg. Cystic fibrosis - ΔF508

Insertions: eg. Huntington's disease - CAG repeats

Point mutations:

- Silent mutation: does not cause disease, as the substituted base still causes the codon to transcribe the same amino acid.

- Missense mutation: causes another amino acid to be transcribed eg. Sickle-cell anaemia - E6V

- Nonsense mutation: causes a premature stop codon to be transcribed, thereby truncating the protein eg. α thalassemia

These mutations only occur on a small scale and can still have disastrous effects, whereas there are some mutations types that occur on a large scale, such as:

Amplifications / gene duplications

Chromosomal / whole gene deletions

Loss of heterozygosity