Personal genomics : review


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2008 was the year of personal genome sequencing. DNA research still has a long way to go, but is now advanced enough to determine with reasonable certainty the carrier status of some genetic diseases (like cystic fibrosis, haemochromatosis or sickle-cell anemia) or the lifetime risk for some more common medical conditions, such as diabetes, celiac diseases, psoriasis, Alzheimer's disease, cardiovascular problems, or even some types of cancer.

In addition one can also learn more about his or her ancestry, or compare specific genes (e.g. immune system, circadian rhythm, sense of taste) with family or friends.

Contrarily to common belief, very little is known of the whole human genome. A DNA test can tell you with 99% certainty if you have blue or brown eyes, but the accuracy drops once people have mixed eye colours, or unusual shades.

Researchers still don't have a clue of many genes are involved in body height. Some SNP's are know to have an influence of a few centimetres or millimetres on height. That alone won't tell you who is taller between 2 individuals. Too many SNP's are still missing to get the big picture. Add to that the environmental factor. Height depends a lot on nutrition, not just genes. The same is true for many diseases. Eating healthy will help you reduce the risk of heart diseases, obesity and diabetes. The point of personal genomics is justly to know what are one's risk in order to adapt one's lifestyle in consequence.

Eating right won't help you for rheumatoid arthritis or breast cancer. But knowing that one is at risk is the key to early detection and higher chances of successful treatment.

How to do the test ?

No blood need to be taken. A simple saliva sample collected in a testing kit and sent to the lab suffice. Technology has evolved dramatically over the past few years. Many genetic genealogy companies specialising in Y-DNA in mtDNA testing will take several months to test just a few SNP's. The big innovation has been to create chips that can read hundreds of thousands or even millions of SNP's in just a matter of weeks (3 weeks being the average, it seems).

Google-sponsored 23anMe has become the most popular testing company since it lowered its price for the full service at 399$ in September 2008.

For this price they test about 600,000 SNP's (the base pairs that represents the "characters" of a DNA sequence). That is still not much when we know that a whole human genome contains 3,000 million base pairs. But these are carefully selected SNP's. Let us not forget that we share 98% of our DNA with chimpanzees, and 99.9% with any other human being.

It is that 0.1% of difference that makes us unique, but also carries higher risks for some diseases or neurological conditions. In fact, 600,000 still is a huge number. In the 100 or so reported conditions and traits, only one to a dozen SNP's are used for each condition. That means that less than 2,000 SNP's are really of any use at the moment.

Things will evolve. New SNP associations are discovered all the time. 23andMe regularly adds new conditions whenever they judge that they are reliable enough (meaning reported independently by several studies). For instance, in January 2008 there were 20 conditions in their reports. There are now 96 of them.

Using SNPedia (a sort of Wikipedia for genes and SNP's) one can learn about hundreds of other conditions, although with a lower reliability. Eupedia has compiled a list of traits and medical conditions with their associated SNP's that makes the research process easier.

23andMe's main rival is DeCODEme, which test a bigger part of DNA (over 1 million SNP's) but still for 999$. Navigenics tests over 2 million SNP's, but remains more exclusive at 2,500$ per test.

Related articles

New Scientist - Me and my genome

TIME - Invention of the Year Nr 1 : The Retail DNA Test

Genetic Future - Personal genomics in 2008: the year in review

New Scientist - News review 2008: Human genes become commodities

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