Guide to Genetic Testing

DNA testing is everywhere these days, from ancestry tests to genetic tests that can tell you if you have genetic mutations and disease risks.  It’s become so commonplace that we take for granted how new the scientific understanding of DNA is and how quickly it is changing.

With so many new companies and services to choose from, it can be a daunting task to find the best company; and once you have the results, it can be difficult to understand what the jargon actually means for you.

We’ve put together a comprehensive guide to genetic testing for health (a.k.a. “genotyping”) and reviewed 4 of the most popular genetic testing for health tools, with website tutorials to help you navigate the software.  We’ve also answered common questions about the accuracy and legality of DNA tests and how to keep your information safe.  We’ve also put together a list of resources to help you find genetic guidance after testing, so you can make informed decisions about your health.

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What is genotyping?

Genotyping is not the same as DNA testing for heritage/family tree or paternity.  Genotyping is an analysis of genetic variants specific to an individual, identifying genetic markers called SNPs:  single nucleotide polymorphisms.  Genotyping focuses on specific, selected genetic markers; whereas gene sequencing focuses on a string of DNA and is not offered to consumers at this time.

Genotyping is a process which requires a DNA sample and is usually done through the use of genotyping chips.  These chips are focused on pre-selected variants to which they correspond; therefore, not all genotyping chips tests for the same variants, and there can be differences between companies and tests offered.

History

History of DNA

Despite the way we banter about DNA in casual conversation, and how easy it is to receive a home DNA test within the last decade, the science and history of DNA is much more complex.  The rise of the consumer genetic test and “direct to consumer” genetic testing, along with the ease and simplicity of acquiring our own genotyped results, belies the complicated truths about DNA.

Our current scientific understanding of DNA has only been present since 1953–a mere sixty-six years ago from when this article was published.  Though it is now a commonplace sight, the logos and background graphics of the double-helix structure you find on many consumer genetic test boxes is a relatively recent discovery that we owe to James Watson and Francis Crick.

Watson and Crick built upon the foundations of four other scientific advances that made it possible for them to discover DNA’s structure:  the x-ray crystallography technique spearheaded by Rosalind Franklin; the belief that DNA in chromosomes were the sole contributors to heredity; the discovery of the equal base pairs in DNA sequences by Erwin Chargaff; and the discovery that protein molecules have helical shapes by Linus Pauling.  By 1966, the complete sequence of a DNA codon was discovered, and the familiar sequence of three adjacent nucleotides as amino acids building blocks of DNA was established. [1][2]

History of Genetics and Genetic Testing

The pioneering advances in the study of DNA, led by Watson and Crick and the scientists who contributed before them, enabled us to have a better understanding of the sequences which determine so much of our genetic fates.  However, the limitations of our understanding of DNA is still being challenged; most of what we refer to as “genes” only accounts for one percent of all of the DNA in our bodies. 

As of a 2012 publication by the Genetic Literacy Project regarding the human genome (or complete set of genes in an organism), scientists believe that less than ten percent of our genome is functional and actively contributes to the genetic factors that are inherited.  The other ninety percent of the genome is not understood at this time.  Some theorize that it is “junk” consisting of biologically neutral material; some of which is retained fragments of inactive or dead viruses that our very, very distant ancestors encountered in the past.

Other scientists prefer to call the other ninety percent of DNA, which, at this time, appears to serve no purpose, “noise.”  The most specific explanation for the remainder of material in human DNA can be thought of as parasites at the molecular level:  transposons.  Transposons are pieces of DNA which can jump around in a host.  Transposons can also be found in plant DNA.  The human genome contains upwards of fifty percent transposons (a large percentage when compared to some plant DNA which contains as little as 2.5%).   [3]

While the specifics and understanding of DNA is relatively recent, the theory and practice behind genetics has been in use much longer.  In 1865, Gregor Mendel discovered the fundamental laws of inheritance, which established that characteristics of organisms were due to an inheritance of genes.  From there, other scientists discovered the number of the human chromosomes is forty-six, and as the technology of the late twentieth-century advanced, so did the field of genetics.   [2]

The Human Genome Project was launched in 1990 and mapped the entire human genome, improving genotyping and gene sequencing techniques along the way.  As genotyping techniques improved, the implementation of direct to consumer (DTC) genetic testing was made possible.  Prior to the flood of direct to consumer genetic tests in the last decade, genetic testing was performed under a physician or genetic counselor.   [2]

Direct to Consumer Genetic Testing History

Direct to Consumer (DTC) Genetic Testing began around the year 2000 with now-extinct company GeneTree, which was sold to Sorenson Molecular Genealogy Foundation and was then passed onto Ancestry.com.  Family Tree DNA began their business in partnership with the University of Arizona to provide DTC testing for genealogy with Y-DNA and mitochondrial DNA tests.

The first company to provide DTC genetic testing through a saliva sample was 23andMe in 2007.  23andMe pioneered using autosomal DNA (which is now used by most, if not all, DTC companies) and offered only ancestry testing at that time.   [4]

Since the inception of DTC genetic testing, there have been many companies that joined the DTC testing movement.  Some of these companies are no longer functioning, and some have been bought up or partnered up with other businesses and brands.

What can genotyping tell me?

There are some things that genotyping can tell you, and some things that are outside of its realm.

Genotyping can:

  • Estimate risk for diseases
  • Tell you if you are a carrier of a disease
  • Provide personalized health information and trait information
  • Make you more aware of better choices for your health

Genotyping cannot:

  • Tell you if you’re going to develop a disease with any certainty
  • Tell you if you’re going to develop a cancer with any certainty

To many people seeking DTC genetic testing, it may not make a lot of sense that genotyping can estimate a risk for a disease but is not capable of telling you whether you may actually acquire that disease.  The reason for this lies in the many factors which contribute to an individual acquiring a disease.

There are many factors that influence whether an individual will acquire a disease, such as age, gender, diet, exercise, individual and family medical history, and ethnic background.  Genotyping can only tell you that you have genetic variants that have been associated with particular diseases.  This does not mean that if you have the variant you will acquire the disease, and likewise, it cannot tell you that because you did not have the variant that you will not acquire the disease. 

The extent of genotyping for disease risk is an estimation; it is a pattern of variants which are a common link between people who have acquired a specific disease(/s).  Keep in mind that even though there is a pattern of commonality between people who share a disease, it does not offer any information on what factors in those individuals’ lives also contributed to the disease acquisition.

The best thing that can come out of genotyping for a disease risk is that you discuss your results with a doctor or genetic counselor and become more proactive and interested in advocating your own health.

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