Understanding Your Genes: Personal DNA Testing
Personal genomics services offer a glimpse into your own DNA profile, a chance to learn about the genetic variants
that distinguish make you different from other people. A growing body of knowledge about human genetics, coupled
with incredible advances in DNA tecnology, have made personal genetic testing a reality. Three companies have
come to the forefront as providers of such services. Which company you choose depends largely on how much you
want to know, and how much you're willing to spend.
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In the past year, 23and me has not only enjoyed substantial media attention, but dropped its price to become
the lowest-cost personal DNA testing option on the market. Its market position and Gene Journal make 23 and
me perhaps the most consumer-friendly personal genomics company.
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The deCODEme has a unique advantage in that it contributes to much of the primary research in human genetic
associations. In October 2008, for example, deCODE scientists published two high-profile studies of the
genetic variants underlying skin cancer.
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Navigenics has a somewhat different approach in that it has an exclusively medical focus, with less emphasis
on direct-to-consumer marketing and more emphasis on actionable conditions. With a price
tag of $2500, this is the priciest service of the three.
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The Genotyping Technologies
All three of these personal DNA testing services use high-density genotyping arrays to interrogate markers throughout
the genome. In most cases, these markers are single nucleotide polymorphisms (SNPs) - single bases in the genome
that vary between individuals. SNPs are the most common form of DNA sequence variation in humans; over 11 million
exist in public databases. Recent efforts led by the International HapMap Consortium used SNPs to construct a
high-density genetic map of the human genome. This haplotype map, or hapmap, makes it possible to selectively
genotype the most informative SNPs and still capture most variation in a person's genome.
23andMe uses the Illumina HumanHap 550+ BeadChip to interrogate 550,000 genetic markers. deCODEme uses an even
higher-density Illumina array, called the Human1M BeadChip (1M stands for 1 million). Navigenics also genotypes
samples for over 1 million SNPs, but on a competing platform, the Affymetrix Genome-Wide Human SNP Array 6.0.
What Your Genes Can Tell You
No matter which service you choose, the volume of data that you get back is substantial.
Ancestry
The frequencies of many gene alleles differ significantly between continental populations. It therefore becomes
very feasible to determine your ancestry by looking at these ancestry-informative markers (AIMs).
Traits
While much of the genetic factors underlying human traits are still unknown, personal gene testing can still tell
you a lot. The variants that affect hair color, eye color, blood type, and even male-pattern baldness, for example,
are well-studied and can be assessed as part of your genetic profile.
Disease Susceptibility
Perhaps the most important yet difficult question to answer is: what does my DNA tell me about my chances for certain
diseases?
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