Michael R. Barnes & Gerome Breen 
Genetic Variation 
Methods and Protocols

"Your genome is an email attachment" What a difference a few years can make? In 2001, to a global fanfare, the completion of the frst draft sequence of the human genome was announced. This had been a Herculean effort, involving thousands of researchers and millions of dollars. Today, a project to re-sequence 1, 000 genomes is well underway, and within a year or two, your own "personal genome" is likely to be available for a few thousand pounds, a price that will undoubtedly decrease further. We are fast approaching the day when your genome will be available as an email attachment (about 4 Mb). The key to this feat is the fact that any two human genomes are more than 99% identical, so rather than representing every base, there is really only a requirement to store the 1% of variable sequence judged against a common reference genome. This brings us directly to the focus of this edition of Methods in Molecular Biology, Genetic Variation. The human genome was once the focus of biology, but now individual genome var- tion is taking the center stage. This new focus on individual variation ultimately democ- tizes biology, offering individuals insight into their own phenotype. But these advances also raise huge concerns of data misuse, misinterpretation, and misunderstanding. The immediacy of individual genomes also serves to highlight our relative ignorance of human genetic variation, underlining the need for more studies of the nature and impact of genetic variation on human phenotypes.