Mutations...linked to cancer!
- Unrepaired DNA (lesion) → MUTATION! → CANCER!
- Change in base sequence of DNA, which if replicated and transmitted to future generations of cells, becomes permanent.
- Mutation → "permanent" change in nucleotide sequence of DNA
- Substitution mutation → Replacement of one base pair with another (e.g. C with G)
- Addition or deletion mutations → one or more base pair added to deleted!
- Silent mutation → If mutation affects nonessential DNA or if it has negligible effect on the function of a gene.
- Rarely a mutation causes some biological advantage, mainly nonsilent mutations are neutral or deleterious.
- In mammals there is a strong correlation between accumulation of mutations and cancer.
- Bruce Ames measured potential of given compound to promote certain easily detected mutations in a specialised bacterial strain.
- Few chemicals encountered in daily life score as mutagens in this test.
- The compounds known to be carcinogenic from extensive animal trails, more than 90% als found to be mutagenic in the Anne test.
- Because of this strong correlation between mutagenesis and carcinogenesis, the Anne test for bacterial mutagens is widely used (rapid and inexpensive) screen for potential human carcinogens.
- In absence of repair systems, the cumulative effect of many infrequent but damaging reactions would make life impossible!