The age of consumer genomics has arrived. Nowadays, you can send a great deal of whatever you are looking for 23andMe and AncestryDNA, both with more than five million users in their databases, are widespread and popular companies in this market analysis ancestry, and the largest of these. These numbers dwarf the numbers of human genomes in scientific databases. Genetic genealogy is big business, and has gone mainstream. But how accurate are these tests truly?
First, a bit of genetic 101. DNA is the code in your cells. It is the richest but most complex treasure trove of information that we've ever attempted to understand. Three billion individual letters of DNA, roughly, organized into 23 pairs of chromosomes-although one of those pairs is not a half-time (men are XY, women are XX). The DNA is about 20,000 genes (even though it remains about what the definition of a gene actually is). And rather than genes, almost all of your DNA-97 percent is a smorgasbord of control regions, scaffolding and huge chunks of repeated sections.
Modern genetics has unveiled a picture of immense complexity, one of which we do not fully understand-although we are certainly a long way from Mendel and his pea experiments, which first identified the units of inheritance. Throughout the process of biological inheritance: how do you encode the genes?
By 2003, the Human Genome Project had been delivered to the Human DNA Sequence in its entirety. One of the most important products of that endeavor is the advent of technology that allows us to read DNA at unprecedented speed and for ever-decreasing costs. We can now pump out the genomes of hundreds of thousands of people for peanuts, and with that data comes greater and greater perspicacity into the profound questions of inheritance, evolution and disease. There's an infinite variation in human genomes, and scrutinizing our DNA helps us to understand what makes us human as well as individuals.
All of a sudden, any company could set up shop, and in exchange for some cash and a vial of saliva, could extract your DNA from the cells into your mouth and sequence your genome. Alongside the behemoths 23andMe and AncestryDNA, dozens of companies have done just that.
There are two potential issues arising from the question of their results' accuracy. The first is somewhat trivial: Has the sequencing been done well? In critiquing this business, it seems fair to assume the data generated is accurate. But there have been some bizarre cases of failure, as the company failed to identify the sample DNA as coming from a human, but from a dog. One recent analysis found that "direct to consumer" (DTC) genetic tests were performed.
Assuming the tests are done accurately, some discrepancies can still arise from differences in the companies' DNA databases. Almost every DTC genetic test does not sequence your entire genome, but instead looks at it in your DNA that are known to be of interest. When I was tested by 23andMe, they proclaimed I do not carry a version of a gene that is associated with red hair. Another ancestry company said I did.
If we take the data generated is accurate, then the second question is that on the interpretation. And this is where it gets murky. Genome Wide Association Studies, or GWAS (pronounced gee-woz), is widely known. Take a bunch of people, as many as possible, have a shared characteristic. This could be a disease, like cystic fibrosis (CF) or a normal trait, say, red hair. When you sequence all of your genes, you look at each other in your DNA. For CF, you would see a big spike in chromosome 7 because of the fact that CF are caused by a mutation in one gene. For redheads, you'd see 1
Genetics is a probabilistic science, and there are no genes "for" anything in particular. I have severe reservations about the utility of genetic tests that indicate one's individual propensity for certain conditions outside of a clinical setting; If you do not have a PhD in genetics, these results can be misleading or even troubling. Alzheimer's disease, which is profoundly influenced by many lifestyle choices and some blind luck.
When it comes to ancestry, DNA is very good at determining close family relations such as siblings or parents, and dozens of stories are emerging or reunited or identify lost close family members (or indeed criminals). For deeper family roots, these tests do not really tell you where your ancestors came from. They say where DNA like can be found on Earth today. By inference, we are to assume that significant proportions of our deep family came from those places. But to say that you are 20 percent Irish, 4 percent Native American or 12 percent Scandinavian is fun, trivial and has very little scientific meaning. We all have thousands of ancestors, and our family trees become matted webs as we go back in time, which means long before our ancestors become everyone's ancestors. Humankind is fascinatingly closely related, and DNA wants to tell you little about your culture, history and identity.