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Genes & Disease
Personalised drug treatment using SNP's
99.9% of our genes are identical to anyone else's. The other 0.1% that makes us unique is made up of 3 million single nucleotide polymorphisms (SNPs) that occur one in every 1000 bases.
A SNP is a variation of one nucleotide between the DNA sequences of individuals. Ten pharmaceutical companies and the Wellcome Trust have set up the SNP consortium to compile a SNP map of 300,000 SNPs. The rationale behind this giant venture is that the SNP map can be used in the mapping of disease associations and can also be used to unravel an individuals response to various medications. The most interesting SNPs from a pharmaceutical point of view are the coding-SNPs (cSNPs).
These occur in coding regions and are therefore themselves either directly responsible for the disease or a different drug response when they cause a non-synonymous change to a protein.
Pharmacogenetics is the study of the genetic basis for the difference between individuals in response to drugs in order to tailor drug prescriptions to individual genotypes. SNPs can be used to distinguish between patients who will benefit from a particular drug against those who will not. This ability to divide the population into drug responders and non responders makes it possible to target a specific population that would benefit from a new drug more effectively. The result will probably be a significant increase in the chance of getting a new drug through to market. This new approach defines a new discovery paradigm that moves beyond genomics to personalised drug treatment.
The information obtained from these polymorphic studies could be used in target validation. If a target is determined to be highly polymorphic, it could be abandoned. Drugs that were abandoned because they caused severe side effects in a minority of people, could be revived.
It is believed that in the future doctors will use "SNP-chips", tiny microarrays studded with the DNA sequences that bind to different SNPs. A patient's DNA would be washed over the chip and fragments that matched the sequence would bind to the chip and light up. With computer analysis, doctors would know which gene variations each person carried. Given this head start, they could intervene, long before the disease began to manifest or they could determine which medication would besr suit that individuals genetic makeup.
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