Monday 29 September 2003
Definition: A mutation can now be defined as a permanent change in the DNA. Mutations that affect germ cells are transmitted to the progeny and may give rise to inherited diseases (germline mutations). Mutations that arise in somatic cells understandably do not cause hereditary diseases but are important in the genesis of cancers and some congenital malformations (somatic mutations).
splice site mutations
Effects of protein mutations
protein loss of function
According to the function of mutated protein
lack of transport to cell membrane
anomalies of glycosylation
disease-predisposing mutations (genetic predisposition)
disease-causing mutations (genetic diseases)
Mutations can cause either the deficiency or the inactivity of a protein.
Many diseases arise from mutations that primarily affect neither expression nor function, but result in a protein with decreased conformational stability.
This conformational instability can intermittently cause the affected protein to unfold and then undergo intermolecular linkage, which results in intracellular aggregation that causes cumulative cell damage.
The insidious nature of protein accumulation explains why some familial diseases characteristically affect individuals in middle- or old-age.
The aggregation of conformationally destabilized proteins is now known to be a feature of many of the neurodegenerative diseases, notably of Alzheimer and Parkinson diseases and the spongiform encephalopathies. (see serpins, serpin family of protease inhibitors).
The common consequence of the mutations in all these diseases is the molecular instability of the encoded protein, which results in the formation of intermolecular beta-linkages, in which single peptide strands become aligned to form highly stable beta-sheets. These beta-linked structures then accumulate to cause cell death and hence disease.
- disease-causing mutations
- disease-predisposing mutations
mutations in a gene causing different disorders