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
https://tinyurl.com/yclx8o2o

MIT Technology Review article on gene testing
https://tinyurl.com/yyfhsnd8

On the workings of microarray tests:

OPEN – A general look at microarray assays
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4011503/

A description of the Illumina BeadArray chip
https://www.ncbi.nlm.nih.gov/pubmed/17225249

A short description of the Illumina protocol for microarray testing
https://tinyurl.com/y257axzf

A thorough description of the Illumina protocol for microarray testing
https://tinyurl.com/yxuezrlb

Ancestry testing

An article by Science News on ancestry testing
https://www.sciencenews.org/article/dna-testing-ancestry-family-tree

OPEN – A review on genetic ancestry testing and its implications
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2857388/

A page on the International Society of Genetic Genealogy wiki comparing the different consumer directed tests
https://isogg.org/wiki/Autosomal_DNA_testing_comparison_chart

OPEN – A look at the software behind ancestry gene testing
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3542037/

OPEN – A study describing the accuracy of reference populations used for ancestry testing. Also general information on ancestry testing
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4101176/

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.
https://www.ncbi.nlm.nih.gov/pubmed/23440589

Consumer directed DNA testing for health

OPEN – A critical look at consumer directed health risk tests
https://www.nature.com/articles/s41436-018-0097-2

An article by Science News on the limitations of consumer health risk tests
https://www.sciencenews.org/article/health-dna-genetic-testing-disease

A critical New York Times opinion on 23andMe
https://www.nytimes.com/interactive/2019/02/01/opinion/23andme-cancer-dna-test-brca.html

A look at the landscape of consumer directed gene tests
https://onlinelibrary.wiley.com/doi/abs/10.1002/ajmg.c.31603

OPEN – The study finding false positives in raw data. Also outlining the limitations of consumer health testing in general.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6301953/

23andMe’s response to the false positives finding
https://www.nature.com/articles/s41436-018-0094-5

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

Hi Reddit! We’re representatives from personal genetics companies and the DNA Discussion Project and are here to talk about at-home genetic testing and what it means for you. Ask us anything! from science

NIH take on the raw data
https://ghr.nlm.nih.gov/primer/dtcgenetictesting/dtcrawdata

On sequencing technologies and clinical gene tests

A description of gene testing in the clinical lab (Diagnostic Molecular Genetics, chapter 6)
http://www.sciencedirect.com/science/article/pii/B9780128125366000067

A review on medical gene testing looking at both microarray and sequencing methods
https://www.ncbi.nlm.nih.gov/pubmed/23681062

A new review on the developments of genetic medicine
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6399103/pdf/cs-133-cs20180436.pdf

Credits:
Family portraits:
https://tinyurl.com/yxoh5f7l Attribution 2.0 Generic (CC BY 2.0)
https://tinyurl.com/y5hvqjcb Attribution 2.0 Generic (CC BY 2.0)
https://tinyurl.com/yy3m4p5t Attribution 2.0 Generic (CC BY 2.0)

50e note: https://tinyurl.com/y3kmbogp Attribution 2.0 Generic (CC BY 2.0)
Old map: https://tinyurl.com/y4z6emg9 Attribution 2.0 Generic (CC BY 2.0)

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