23andMe offer direct-to-consumer
DNA analysis. Customers order a collection kit over the internet - essentially
a tube you spit into and return to the company. About six weeks later the
results arrive by email. At no point is there any involvement from a physician
or genetic counsellor to explain what is being tested for or the consequences
of the results.
23andMe use a
single nucleotide polymorphism (SNP) array that tests for markers in five
different categories: genes leading to inherited conditions, genetic risks,
traits, genes affecting drug response and ancestry. The service costs £125 per
person. I think most people taking this test are going to assume that nothing
will show up - as I did.
are very complex, even when there's just one faulty gene involved. For example,
over 1,000 different mutations can give rise to cystic fibrosis. 23andMe only
tests for one or a few mutations in each gene, so using this test does not mean
that you are not at risk of the disease they are testing for.
diseases are multifactorial; they can be affected by both genes and environment,
and some disorders show varying penetrance, so carrying the faulty gene does
not necessarily mean you will get the disorder. As you can see, it's complicated.
All of the 43
inherited conditions in this test are recessive, so to have the disorder you
would need to inherit two faulty genes; one each from your mother and father. The
majority of the disorders they test for are early onset, so any adult taking
the test should already know that they have the condition. Included in the 43 genes are a large number of
very rare inherited conditions for someone with a European ancestry, such as
Gaucher disease and maple syrup urine disease, both of which are common in
those of Ashkenazi Jewish ancestry.
Eleven genetic risk
genes are tested by 23andMe, including Alzheimer's, Parkinson's, and the breast
and ovarian cancer risk genes BRCA1 and 2.
In my view, 23andMe
should not include these three disorders on their genetic testing panel. Due to
the potentially life-altering nature of the test results, 23andMe have 'locked'
these results, but unfortunately this only means that you need to do two extra
clicks to gain access. Once you know your genetic status for these disorders,
the information cannot be taken back.
The 23andMe test for
the BRCA1 and 2 genes are unlikely to be positive for someone of European
decent as they only test for the three common mutations affecting Ashkenazi
Jews. Also, the majority of breast cancer is not genetically inherited and so
even if someone is free of BRCA1 and 2 mutations, it does not mean you will not
get breast or ovarian cancer.
Parkinson's is a
serious disorder of the brain's motor centre and current treatment is effective
in few people but only ever serves to slow the disorder, not cure it. A friend recently
diagnosed with Parkinson's told me that he is glad he did not know they were at risk
before their diagnosis.
And then Alzheimer's
has no treatment or cure. I would have preferred to have opted out of receiving
this information but this was not possible.
The other genes assessed in the genetic risk
section are not as controversial and include hypertrophic cardiomyopathy and
inherited thrombophilia (factor V Leiden), which increases the risk of deep vein thrombosis. I discovered
that I was at five times the risk of getting deep vein thrombosis, but I could
not find anywhere what the base value was. I have already been emailed by a company selling
23andMe look at 40
genetic traits which cover a range of random, mainly useless information,
including breast morphology, how many teeth at age 12, birth weight, bitter
taste perception, eye colour, earwax type, age of first period, red hair and
pain sensitivity - you get the idea. I found out I was lactose intolerant and had
increased pain sensitivity, the significance of which is debatable.
The test also
analyses 12 genetic variations related to how people respond to drugs. These
may indicate differences in sensitivity or in the likelihood or severity of
side effects. This is quite complex information, which would need to be decoded
by a physician and is only relevant if you were having a particular drug treatment.
For ancestry, 23andMe
determines what percentage of your DNA comes from 31 populations worldwide. I
found that I was 68 percent European and 28 percent South Asian. This
information can be shared with others on the 23andMe database, anonymously or
named, and some people have found close relatives. I only had third to sixth cousins
in the database.
For me, having my
DNA analysed by 23andMe was an interesting experience but it took me several days
to go through the overwhelming amount of genetic information I was supplied
with (and I know something about genetics!)
I found the web
site difficult to navigate and the information of varying quality. I cannot imagine what a person who knows
little about genetics would gain from this information — confusion, stress,
anxiety? Some of the information is benign, but some is sensitive and cannot be
genetic analysis is on the rise and people should be given the opportunity to 'personalise'
their results so that any unwanted information on genetic disorders or risk is
The Holy Grail will be next-generation
sequencing which can read the full sequence of your genetic code and this is
already offered over the internet. Sequencing is also performed for non-invasive
prenatal testing at around ten weeks of pregnancy (this has not yet been fully
rolled out across the NHS), but currently only looks at a few chromosomes of
the fetus. In the future it should be possible to test the full genome during
pregnancy so every child will be born knowing their genetic code. It is
essential that the role of the genetic counsellor be embraced so that the full
potential of this information is understood.