Only 0.1 degrees of separation

"Although any two unrelated people are the same at about 99.9 percent of their DNA sequence, the remaining 0.1 percent is important because it contains the genetic variants that influence how people differ in their risk of disease or their response to drugs." http://english.people.com.cn/200312/19/eng20031219_130721.shtml

"But it is the 0.1 per cent variation that will be important for determining why some individuals are more susceptible to a particular disease or respond differently to a drug, toxin or other environmental factor.

"The tiny variations the scientists" look for are "sites in the genetic code where the DNA sequence of many individuals varied by a single letter. There are an estimated 10 million of these sites, known as single nucleotide polymorphisms, or SNPS (pronounced snips) in the human population. However, they tend to be inherited in groups, called haplotypes, hence the term HapMap.

"It is a feat akin to sticking a million Post-It notes into the tedious book of 3 billion letters that is the human genetic code, so that the important bits are easy to find." ("Post-It note may hold cancer clue", by Deborah Smith, SMH Oct 27, 2005.)

It appears there is more on this in the new issue of Nature magazine.