When Celera Genomics first sequenced the entire human genome in 2000, the scientific community and the world at large met the news with unbridled enthusiasm'and with good reason. Sequencing the three billion base pairs in human DNA in a little over a year was a staggering achievement.
Unfortunately, like intro-level Spanish students on the first day of class, scientists did not yet know what the majority of these little chemical letters meant.
Piecing together the code was the first stage'understanding it has been a much more daunting task. But with last week's completion of the first phase of the 'HapMap' project, science is getting one step closer to fluency in the language of human genetics.
Published in the Oct. 27th issue of Nature, the HapMap outlines the genetic variation between 269 individuals from areas of Nigeria, Japan, China and the United States. Since humans share 99.9 percent of the same DNA, this study provides insight into the remaining 0.1 percent'the source of all genetic differences within mankind.
This HapMap has the potential to unlock new modes of disease diagnosis and treatment as well as supply new information about human evolution.
'The HapMap is focused on single nucleotide polymorphisms ... which can occur within genes, where they can affect the sequence of a protein, or they can occur outside of genes, or in neighboring genes, in areas where they might change the expression of a gene,' according to UW-Madison genetics professor Allen Laughon,
In both cases, the final trait dictated by a gene may be altered.
SNPs (pronounced 'snips') are grouped into blocks called haplotypes. In an interview with Forbes, Peter Donnelly, one of the authors of the study, explained that SNPs and haplotypes could be likened to five people who ride the same bus every day. Once you find which bus one of the passengers is seated in, you'll know the location of the rest of the commuters as well.
The haplotype theory allowed the HapMap team to analyze genetic variation in only 5 to 10 percent of all the SNPs in the human genome, instead of the full 10 million.
So what's the big deal with these minute changes in the epic, genetic scheme of things? Well, these little changes tend to add up.
'In most cases, [disease] susceptibility is not due to a single change, but multiple changes, possibly many changes,' Laughon said. 'This could apply to susceptibility to cancer, heart disease, diabetes ... even neurological problems ... it is anticipated these susceptibilities will vary quite a bit in severity.'
Right now, there is only a small percentage of people who know that they are genetically at high risk for certain conditions; a susceptibility for breast cancer or Huntington's disease can be diagnosed with a DNA test or an analysis of family history.
'In the future, there will be more,' Laughon said. 'Those folks would undoubtedly want to be somewhat more careful about getting preemptive medical care or diagnosis so they could prevent the onset.'
With the information provided by the HapMap, someday it may be possible to 'fix' a disease-causing gene by replacing the offending DNA with a non-harmful version of the gene. However, gene therapy, the physical manipulation and alteration of defective genes as a means of disease defense, has 'a long way to go,' according to Laughon. Some noteworthy progress in gene therapy has been made in animals, but in human tests, some attempts have been, in Laughon's words, 'disastrous,' leading to the death of patients.
'The benefits of the HapMap work are really more for diagnosis and for learning more about the underlying basis for human diseases,' Laughon said.
With the HapMap's ability to pinpoint disease-causing genes, new therapies may not be far behind.
