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How reliable are genetic ancestry tests?

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How reliable are genetic ancestry tests/genealogical DNA testing?

Ancestry report 23andme family

Sample report from 23AndMe

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What is the technology?

tba

Why would people want to do this?

Learn about family history

Learn about susceptibility to diseases (Parkinson’s, Cancer)

Predicting Side Effects of Pharmaceuticals

Are we really of only the heritage that we think we are from?

If you’re black, DNA ancestry results can reveal an awkward truth, Splinter News, 2016

What companies are offering these tests?

  • 23andMe, personal genomics and biotechnology company, Mountain View, CA

  • Affymetrix

  • AncestryDNA

  • Family Tree DNA

  • MyHeritageDNA

Ethical issues

privacy

genetic counseling

Example: Tay Sachs

Five Things to Know about Direct-to-Consumer Genetic Tests. Johns Hopkins Medicine.

Alzheimer’s Society’s view on genetic testing

How reliable is the interpretation of the data?

Intro tba

How DNA Testing Botched My Family’s Heritage, and Probably Yours, Too, Gizmodo, 2018

How Accurate Are Online DNA Tests? Scientific American

Genetic tests are everywhere, but how reliable are they? Boston Globe

Pulling Back the Curtain on DNA Ancestry Tests. Tufts University

What genetic tests from 23andMe, Veritas and Genos really told me about my health. Science News

What I actually learned about my family after trying 5 DNA ancestry tests. Results Vary Wildly. Science News

Articles from scientific journals

False-positive results released by direct-to-consumer genetic tests highlight the importance of clinical confirmation testing for appropriate patient care. Nature, 2018

How is genetic testing evaluated? A systematic review of the literature. European Journal of Human Genetics, 2018

Why is the interpretation of the data often wrong?

The accuracy of the interpretations will get better over time. But for now they are not great. Why not?

Kristen V. Brown writes:

Four tests, four very different answers about where my DNA comes from—including some results that contradicted family history I felt confident was fact. What gives?

There are a few different factors at play here. Genetics is inherently a comparative science: Data about your genes is determined by comparing them to the genes of other people.

As Adam Rutherford, a British geneticist and author of the excellent book “A Brief History of Everyone Who Ever Lived,” explained to me, we’ve got a fundamental misunderstanding of what an ancestry DNA test even does.

“They’re not telling you where your DNA comes from in the past,” he told me, “They’re telling you where on Earth your DNA is from today.”

Ancestry, for example, had determined that my Aunt Cat was 30 percent Italian by comparing her genes to other people in its database of more than six million people, and finding presumably that her genes had a lot of things in common with the present-day people of Italy.

Heritage DNA tests are more accurate for some groups of people than others, depending how many people with similar DNA to yours have already taken their test. Ancestry and 23andMe have actually both published papers about how their statistical modeling works.

As Ancestry puts it: “When considering AncestryDNA estimates of genetic ethnicity it is important to remember that our estimates are, in fact, estimates. The estimates are variable and depend on the method applied, the reference panel used, and the other customer samples included during estimation.”

That the data sets are primarily made up of paying customers also skews demographics. If there’s only a small number of Middle Eastern DNA samples that your DNA has been matched against, it’s less likely you’ll get a strong Middle Eastern match.

from gizmodo How-dna-testing-botched-my-familys-heritage-and-probably yours, 2018

Further reading

Understanding genetic testing: U.S. National Library of Medicine

 

Learning Standards

HS-LS1-1. Construct a model of transcription and translation to explain the roles of DNA and RNA that code for proteins that regulate and carry out essential functions of life.

HS-LS3-1. Develop and use a model to show how DNA in the form of chromosomes is passed from parents to offspring through the processes of meiosis and fertilization in sexual reproduction.

HS-LS3-2. Make and defend a claim based on evidence that genetic variations (alleles) may result from (a) new genetic combinations via the processes of crossing over and random segregation of chromosomes during meiosis, (b) mutations that occur during replication, and/or (c) mutations caused by environmental factors. Recognize that mutations that occur in gametes can be passed to offspring.

HS-LS3-3. Apply concepts of probability to represent possible genotype and phenotype combinations in offspring caused by different types of Mendelian inheritance patterns.

HS-LS3-4(MA). Use scientific information to illustrate that many traits of individuals, and the presence of specific alleles in a population, are due to interactions of genetic factors
and environmental factors.

 

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