DNA tests are used in murder trials, I would expect them to be damn near perfectly repeatable.
Reading other replies there seems to be a cheaper less accurate tech used for these home testing kits.
Reading other replies there seems to be a cheaper less accurate tech used for these home testing kits.
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 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...
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...
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.