How does DNA testing work (Complete guide)

How does DNA testing work? Ancestry and health risk genetic tests tests provided by companies like 23andMe can tell you about your origins and about mutations that might increase your risk of developing a disease.
Ancestry testing services tell you roughly where you are from. The services cannot tell you precisely where you are from and companies often downplay the uncertainty of ancestry results.
Disease DNA tests sold to consumers are accurate about the mutations they are allowed to report, but they only report a part of the possible mutations.
The DNA tests sold to consumers are microarray tests provided mostly by the genetics giant Illumina. Sequencing technologies for genetic testing are used in diagnostic laboratories and they can provide a full report of the mutations found in the genome.

Resources
General articles

A great general article on gene testing in the Scientific American

MIT Technology Review article on gene testing

On the workings of microarray tests:

OPEN - A general look at microarray assays

A description of the Illumina BeadArray chip

A short description of the Illumina protocol for microarray testing

A thorough description of the Illumina protocol for microarray testing

Ancestry testing

An article by Science News on ancestry testing

OPEN - A review on genetic ancestry testing and its implications

A page on the International Society of Genetic Genealogy wiki comparing the different consumer directed tests

OPEN - A look at the software behind ancestry gene testing

OPEN - A study describing the accuracy of reference populations used for ancestry testing. Also general information on ancestry testing

A thorough look at Genetic genealogy: the analysis of DNA in combination with studies of historical records. By combining these fields, a more in-depth picture of one's past can be constructed. In this video, I did not cover the Y-chromosome and the mitochondrial DNA testing that are also often tested by people interested in their genetic genealogy. With these methods, one can learn more about their direct paternal ancestors (Y-chromosome) and direct maternal ancestors (mitochondrial DNA). As no recombination happens with the Y-chromosome and the mitochondrial DNA, these lineages can be traced a lot further back. However, they are only individual lineages in a family tree with thousands of ancestors.

Consumer directed DNA testing for health

OPEN - A critical look at consumer directed health risk tests

An article by Science News on the limitations of consumer health risk tests

A critical New York Times opinion on 23andMe

A look at the landscape of consumer directed gene tests

OPEN - The study finding false positives in raw data. Also outlining the limitations of consumer health testing in general.

23andMe's response to the false positives finding

23andMe's response in the reddit AMA. The response can be found quite far down the thread. The whole reddit thread is interesting.

NIH take on the raw data

On sequencing technologies and clinical gene tests

A description of gene testing in the clinical lab (Diagnostic Molecular Genetics, chapter 6)

A review on medical gene testing looking at both microarray and sequencing methods

A new review on the developments of genetic medicine

Credits:
Family portraits:

[LcdDrmr]

Excellent in-depth work with no bias or sensationalism, just real science reporting. More channels should be like this one.

[shauryaroy]

It’s interesting how they can find the 1 percent of a 100 DNA that differentiates you from other people.

[EveryCellAUniverse]

Timecodes for the different parts of the video:
01:17 How consumer gene tests work
05:50 Difficulties with ancestry testing
09:32 How family relationships are tested
11:05 The health risk report
14:43 How sequencing technologies work

[EveryCellAUniverse]

A clarification on ancestry testing. In the video, I stated that groups of SNP's that are only shared within a population from the same geographical location. What I should have said is that the SNPs are the same for different populations, but the proportions of those SNPs varies between populations.

[ivandimov]

Great video! Really hepled me with my biology project. Appreciate the hard work put into this!

[AkshanshShrivastava]

This is a great video for someone curious like me to know everything about everything

[gabrieltorres]

Great video! Thank you for all the info!

[KH-mxbg]

Great explanation of direct to consumer genetic tests for a layperson. I’m an undergrad researcher in a genetics lab, and sometimes I find it difficult to explain the mechanics and the limitations to family members when they discuss these types of tests. I will definitely recommend this video to them the next time it comes up.

[rockinkitten]

I’m waiting on my DNA test results, very excited and hoping for some answers which could be life changing 🤞🏻

[SouKube]

Would it be possible to explain this in a family with 5 to 7 generations, even if hypothetical. This might make it clear.

[tejasvis]

Hey, great video! I always watch your content every time you upload :)

[MediaBuster]

Can we see ACTUAL pictures of DNA and how you have determined any of the things you say and not computer graphics, please?

[SpectraVV]

I would suggest adding captions in other languages, so you you can gain the audience who don't understand English (but then I realize that it is hella hard work to do so nevermind)

Anyways, good video!

[faithesprit]

Thank you for this would be great to understand the genetic analysis for suspected genetic disorders and initiated by the pediatric hospital

[MetallicDec]

Can getting thsee tests done show who your real father is, even if that person disnt take, lets say the 23 and me website? Im curious how this works trying to find this answer

[ramadharsant]

D.n.a. test karne wali maseen ko ky bolte hain

[uri-yahu]

Thanks for the scientific explanations instead of just laughing and saying the tests are fake

[sartoriusrock]

Single-strand DNA

Isn’t that the same thing as RNA? Or am I missing something?

[globalko]

Very good video, your accent is accent is really strange it is like a mix of French/Spanish/Scandinavia

[fc]

The narrator is correct to say that there are limitations in detecting ethnicity. Obviously these dna tests won’t always be able to tell the difference between a German and an English person or between a Korean and a Japanese person. But these tests are pretty accurate at getting broad racial backgrounds correct (determining which continent or region someone is from) and whether or not, say, an English person has an ancestor from India from the colonial period or whether or not a Filipino has Spanish ancestry. If there is any mixture that resulted from the colonial period anywhere (the past 500 years which is when most major racial mixture started taking place) this test WILL pick it up. I have been researching how the reference populations are chosen, and they are very precise about. I don’t get how this narrator thinks that a difference between a pure French man and a pure Chinese person is somehow “very difficult to detect”. This pc nonsense about how all races are exactly the same is getting ridiculous.