I havent looked into getting a DNA test at all. But I would expect it to be accurate and repeatable.
>An entire DNA sample is made up of about three billion parts, but companies that provide ancestry tests look at about 700,000 of those to spot genetic differences.
>According to the raw data from 23andMe, 99.6 per cent of those parts were the same, which is why Gerstein and his team were so confused by the results. They concluded the raw data used by the other four companies was also statistically identical.
>Still, none of the five companies provided the same ancestry breakdown for the twins.
So these people getting results and finding out they aren't related to their parents, are the results suspect?
Ditto the results about genes associated with dementia or heart disease?
I'm aware of the companies having disclaimers, I thought that was on the basis of them not really know what the genes did, not that the test itself was rubbish.
Is it a case of them adding too many decimal places to the percentages? Making statistics out of noise?
These SNP arrays, however, are exceedingly accurate and reproducible in their calls. A common medium-density SNP array used for human genetics is the Illumina CytoSNP-850K [1], which routinely gets >99.5% accuracy on calls. This is at least as good, or better than, whole genome sequencing.
The challenge in ancestry assignment is not determining what is in the sample, but rather in the interpretation and assignment of ancestral haplotypes.
[1] https://www.illumina.com/content/dam/illumina-marketing/docu...
>99.5% accuracy is great for a scientific measurement device that's only been developed very recently; it's absolutely rubbish if you want to sell the results to consumers.
Or potentially put people in jail based on these results...
You can get considerably better accuracy, you just have to be willing to fork over $1500 rather than $60. How much are you willing to pay to know if your 31% German vs 30%?
There was a good 5-10 years where microarrays were the go-to method for genomic investigation. Since RNA-seq has supplanted it, there has been no revolution in overturning those old results. At best, RNA-seq reveals what microarrays cannot: novel sequences, specific sequences that have difficulty hybridizing, etc.
The variation between these services is due primarily to how the data is interpreted and presented to customers, not the reads themselves.
In this case "SNP microarray" is a "digital" (or binary) readout of the genomic DNA sequence; specifically the array has attached to it sequences that match both the "reference allele" (e.g., a "G") and the "alternate allele" (e.g., "A" or some other base). Note that across the world's population, most sites in the human genome are "bi-allelic" meaning that there's really only two variants at each site, though of course it is possible to have tri-allelic or even fully polymorphic (A, T, C, or G) sites. For the purposes of ancestry, bi-allelic identification of commonly polymorphic sites is adequate, though the more sites and the rarer those sites are in world populations, the more specific you can be re: ancestry. This is why the gold standard for ancestry and haplotyping is whole genome sequencing-- you simply get far more informative sites to map to other populations.
When my doctor asks how tall I am, if I'm 6'1", then 6'1" is a good answer. 6' (or even better: about 6') can also be an acceptable answer, as it's an approximation. I wouldn't say I'm 6'8", and then try to rationalize it by saying my tape measure is cheap, and anyway it's still right to about 10%.
Reporting what you don't know can be just as important as reporting what you do know. It doesn't matter how good your laboratory method is if you can't report results in a way that doesn't mislead customers.
And there's a difference between "not perfect" and "doesn't provide the same result twice".
"doesn't provide the same results twice" is the honest acknowledgement that the concept of perfection is itself what is flawed here because it creates false expectations of what science can give us in this arena
The accuracy of the broad conclusions drawn from population wide samples about any single individual’s ethno-historical origins is a falsehood that science cannot ethically or logically support
Not getting the same result twice is pretty much 100% failure :-)
Frankly I am skeptical that they could even ascertain any semblance of your heritage but I'm definitely a layperson.
Reading other replies there seems to be a cheaper less accurate tech used for these home testing kits.
Basically all forensic science has turned out to be crap or misapplication of good science except for DNA which a) exonerates a heck of a lot of people and b) was a concept that matured in biology before being adopted by forensic scientists.
So are other forensic methods, like fingerprint[1] and hair[2] analysis. Turns out that forensic evidence isn't very scientific nor accurate.
[1] http://theconversation.com/fingerprinting-to-solve-crimes-no...
[2] https://rss.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1740-9...
DNA fingerprinting involves:
* Sequence amplification of polymorphic sites by a panel of well-characterized primers, many of which cross-check each other by amplifying over the same locus.
* These amplicons are then characterized by size via restriction digest and simple electrophoresis. No sequencing is performed, only the length of the DNA fragments is characterized.
* Due to population-level variation of short-tandem repeats, analysis of ~20 loci can uniquely identify an individual with a desired level of statistical confidence. The kind of data used to confirm a match in e.g. a murder trial will be absurdly robust.
DNA fingerprinting is limited by the quality of sample collection and handling (i.e. don't mix up or contaminate samples), but not the accuracy of the method.
Even sequencing a genome is not perfect - the current most common method works by cutting the genome into pieces, sequencing those and then reassembling them. A pretty obvious limitation is that you can't detect repeated sections.
I'm not sure what method the police use but it definitely isn't the same as what 23andme do.
So were the results of FBI hair and fiber analysis, and look how that turned out.
https://www.washingtonpost.com/local/crime/fbi-overstated-fo...
So I picked up a mid-range automatic bp cuff, and started to measure it more regularly. The numbers were all over the place and completely unrepeatable unless I maintained exactly the same position/breathing/etc. I can literally swing my BP by 30+ mmHg, by re-positioning my body, drinking a cup of coffee, etc, all while officially still maintaining proper technique for measuring it. And yes, moving up a cuff size also tends to remove a ~5mmHg from my measurement.
I could write a book about how to get any BP you want out of the machine. Its the same with weight, I can shift my weight +-10% by eating a bowl of salty popcorn drinking a few 64oz cups of ice tea, then eating a large meal. Then I can go for a 3 hour bike ride, use the toilet and drop it all back off.
So, its sort of surprises me the fine grained aspect of DR's always measuring your BP/Weight, neither of which really mean anything until they get into the extreem ranges, and in the weight case you can get a better feel for it just by looking at someone...
We would schedule people for Nurse only BP checks to help establish the pattern.
This statistical anbiguity is why the medical community as a whole is often sceptical of the Direct to consumer DNA testing and SNP analysis. They report data in a convincing way which is statistically misleading and in no way plainly reveals what is within measurement error.
You're not going to get a very high degree of accuracy from a ~$100 test. They're not sequencing your entire genome for that amount of money. It is still good enough to determine the broad strokes of someone's ancestry, to within a few percentage points as you see in the linked article.
If you're willing to pay for full sequencing then you're going to get a lot more accuracy and repeatability. You're also going to pay a lot more for it than would be warranted just to satisfy your curiosity as to where your ancestors came from. These kinds of tests would really only be warranted if you have some rare, difficult-to-treat genetic disease. That might not even help you directly, but rather, be done to contribute to the body of scientific knowledge of the disease.
If you do it 10 times, you will always get the same buckets, but the percentages will differ back and forth for a bit. If you're goal it so find out your heritage, which these services are offering, then you are getting the right heritage repeatedly.
If your goal is to find out how many 0.1% of you is of an exact descendance, then you're going in with the wrong expectations.