By calculating probabilities and doing extensive lab tests, Crooke surmised that a 20-nucleotide sequence was optimal.

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But DNA chip technology for scanning these so-called single nucleotide polymorphisms, or SNPs ("snips"), was prohibitively expensive in 2000.

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The scientists looked for common genetic variations - known as single nucleotide polymorphisms (Snps) - linked to the three cancers.

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These small mistakes are called single nucleotide polymorphisms, or SNPs.

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To prevent his drug from degrading in the body, Crooke tinkered with the phosphate bonds between each DNA nucleotide, replacing one of the oxygens in each bond with sulfur.

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Enormous efforts have gone into examining the contribution of other normally-occurring genetic variants (single nucleotide polymorphisms, or SNPs), but these studies have only identified a few SNPS with very slight increases in risk.

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As a first step, the scientists examined half a million genetic markers in the participants' DNA. These markers, known as single nucleotide polymorphisms, or SNPs, can together reveal how genetically similar people are, even though they are not conventionally related.

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It focused narrowly on areas in and around active genes, ignoring the 98.5% of genomic material known as "junk DNA." This process pinpointed 25, 000 genetic landmarks called SNPS (single nucleotide polymorphisms, or "snips"), places where a single dna letter varies from one person to the next.

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