Point Mutation

A point mutation or substitution in DNA research involves a mutation where the replacement of a single base nucleotide is made with another nucle-otide—nucleotides being the chemical compound that is found in the structural units of DNA. Essentially, the mutation involves the insertion or deletion of a single base pair, which can have, or may lead to, a more-than-adverse effect on any synthesized protein owing to the nucleotides being read in triple sequences.

Three levels of mutation are involved. The first, nonsense mutations, are a code for a stop, which can truncate the protein. A silent mutation involves the use of the code for the same amino acid, and a [Page 1388]missense mutation involves a code for a different amino acid.

These mutations occur spontaneously in DNA replication with the rate being increased by mutagens. These mutagens vary from physical ones and can include exposure to extreme heat, X rays of ultraviolet rays, or chemical ones with molecules that misplace base pairs or disrupt the helical shape of the DNA.

Mutagens associated with cancers have been the subject of much work with many researchers feeling that it might provide them with an opportunity to discover how cancer spreads, and hence, how it can be prevented. Other disorders involving point mutation include the spread of sickle cell disease where a beta hemoglobin gene converts a GAG codon into a GTG which can then encode the amino acid valine rather than the glutamic acid.