There's One Christmas Gift Idea That Could Tear Your Entire Family Apart


Sure, it sounds like a nice idea. Give your loved ones a present that will provide insight into their heritage, potentially connect them with long-lost relatives, and inform them if they carry risk genes for lactose intolerance, weight gain, or serious diseases.  

But we would advise you to rethink doling out direct-to-consumer (DTC) DNA test kits, like those offered by Ancestry.com and 23andMe, to everyone on your holiday list. That is, unless the intention of your gifting is to terrify friends with inaccurate warnings about the state of their health or tear your family apart by digging up the type of secrets that should stay buried. It’s your call.

See, as fun as these services might be – who doesn’t want to know how much Neanderthal DNA they have? – the industry behind them is claiming to offer insights that overstep our current understanding of human genetics, and at the same time, creating unprecedented privacy issues that our legal systems have yet to catch up with.

Why They’re Unreliable

Far removed from the costly and time-intensive process of sequencing an entire genome, DTC tests analyze ancestry and health traits by assessing the presence or absence of known DNA sequence variations in certain stretches of the genome. These variants, often different from one another by just a single nucleotide (hence why they are called SNPs: single nucleotide polymorphisms), have become associated with particular ethnic groups or the development of certain diseases based on the results of more far-reaching genetic analyses that were performed in reference populations. For example, scientists who looked at the genomes of Ashkenazi Jews found variants that a percentage of these people carried some of the same variants, and thus, if a new subject has some of these variants, it’s a good guess that some of their relatives belonged to this ethic group.

Similarly, investigations involving people with cancer or dementia have revealed numerous mutations or gene variants that appear to increase the odds that such illnesses will develop.

After determining which of the predetermined variants of interest each customer has, the companies use statistical programs to calculate the likelihood that this unique genetic profile belongs to someone from Scandinavia vs someone from Southeast Asia, or someone with a good metabolism for carbohydrates vs someone who should lay off grains. It’s an estimation at best and misleading nonsense at worst.

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Ancestry estimations based on such data are prone to error simply because inheritance is convoluted and the reference populations used as benchmarks for each major ethnicity are still quite small (though accuracy has improved as more people do the tests and add their DNA to the databases).

Creating health reports with these methods is much more problematic. Most conditions are mediated by a complex interplay of many genes as well as epigenetic changes caused by environmental factors. However, no DTC analyses are capable of taking this into account. None of the current tests look at the status of all the genes believed to be involved with each disease reported on, and in fact, none even sequence the entirety of individual genes.

For these reasons, claiming a DTC test holds answers to one’s medical destiny is a bit like a quack doctor claiming they can diagnose exactly what’s wrong with you based on your runny nose and sore throat. We need to know a lot more about the genetic underpinnings of these diseases before we can determine the consequences of certain variations.

What Could Go Wrong?

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