///DNA Testing

DNA Testing

DNA testing or genetic testing is any test that uses DNA to determine medical traits, ethnic origins, and genealogy. Some companies are using it for lifestyle testing. In genetic genealogy, one may test for any of these reasons or for all of them.

Results can come both from reports provided by DNA testing companies and from reports generated by 3rd Party tools.

Ethnic Origins

Ethnic origins testing is proving to be one of the most popular types of DNA test. Unfortunately, it is also one of the least reliable tests in terms of science to back analysis. Results from autosomal DNA testing can vary wildly between companies and from one 3rd Party tool to the next.

You can test any of the four types of DNA (Autosomal DNA, X-chromosome DNA, Y-chromosome DNA, and mtDNA) for ethnic origins. Each type has advantages and disadvantages. Currently, companies sell X-chromosome DNA with Autosomal DNA tests. Therefore, I will cover these two together and note where the X-chromosome DNA results are not used.

Autosomal & X-chromosome DNA Origins

The main tools provided with any of the autosomal DNA origins are percentage breakdowns and world maps that show population locations. Each company has additional features specific to them such as 23andMe's chromosome painting, Family Tree DNA's Ancestral Origins, and Ancestry's migration groups.

mtDNA Origins

Mitochondrial DNA has been in use for scientific population genetics the longest, and the methods of mtDNA Origins testing are scientifically solid. However, because the mtDNA tree has expanded rapidly in the past five years, origins information for some branches of the maternal tree is completely missing.

Y-DNA Origins

Y-chromosome DNA (Y-DNA) was the second type of DNA used in many published population genetics papers. However, in the past three years Y-DNA testing by the general public has passed beyond what is done in academic labs. Like mtDNA, the science here is robust, but origins information may be missing for many of the newer branches of the paternal tree.

Medical & Lifestyle testing

Medical DNA testing was one of the earliest types of test used. However, they began being sold directly to the public more recently than many genealogical tests. Types of medical DNA testing include:

  • * Birth planning related
    •  – Preimplantation genetic diagnosis
    •  – Prenatal diagnosis
    • – Cell-free fetal DNA
    •  – Newborn screening
  • * Diagnostic testing
  • * Carrier testing
  • * Lifestyle testing (Predictive and presymptomatic testing)
  • * Pharmacogenomics

Of these, genetic genealogists use diagnostic testing, carrier testing, pharmacogenomics, and predictive and presymptomatic testing (Lifestyle testing).

Diagnostic testing

Diagnostic testing can identify the genetic variant or variants causing a health condition. For example, at 23andMe, test results include some of the variants related to lactose intolerance.

Example: Lactose testing at 23andMe

Example: Lactose testing at 23andMe

Carrier testing

Carrier testing is used to detect genetic variants that when present in both parents can lead to a health condition in their children. These are usually variants that are recessive. That means that you have to have two copies of the variant to have the health condition.

As an example, someone with a family history of cystic fibrosis might wish to know if they have one copy of a gene variant that could be passed on.

Below is the 3rd party report from Promethease for one cystic fibrosis mutation.

Example: Promethease report for one cystic fibrosis mutation

Example: Promethease report for one cystic fibrosis mutation

Pharmacogenomics

Pharmacogenomics is used to detect genetic variants that change the way one person reacts to drugs and medications compared to the general population. The seriousness of this type of test is dependent on the medication impacted and the significance of that medication for the individual. Lack of response to a beverage you don't drink or a medication for a health condition you do not have has little significance.

For example, someone can have a fast or a slow caffeine metabolism. This Family Tree DNA ‘factoid' shows caffeine metabolism results.

Example: Family Tree DNA Caffeine Metabolism

Example: Family Tree DNA Caffeine Metabolism

This is the 3rd Party Promethease tool report for the same genetic variant.

Example: Promethease Report

Example: Promethease report for Fast Caffeine Metabolizer

This is another Promethease report for the type 2 diabetes medication Metformin.

Example: Promethease report for response to metformin in type 2 diabetics

Example: Promethease report for response to metformin in type 2 diabetics

Lifestyle testing

Predictive and presymptomatic testing is more commonly refereed to as Lifestyle testing. It is for the detection of genetic variants that predispose you to a health condition such as diabetes, cancer, or high blood pressure but do not directly or always lead to the condition. When aware of the risk, many such conditions can be prevented or minimized through lifestyle changes such as diet and exercise. Others can be detected sooner if monitored.

This is a place where DNA testing science is at the boundary between credibility and wishful thinking. In some cases, the information is important and actionable. In others, it is not.

This is a 23andMe result for Genetic Weight.

Example: 23andMe Genetic Weight report

Example: 23andMe Genetic Weight report

On the other hand, these are reports related to autoimmune disorders from 3rd Party Promethease created with 23andMe data.

Example: Promethease report for Increased Risk of Multiple Autoimmune Disorders

Example: Promethease report for Increased Risk of Multiple Autoimmune Disorders

 

Example: Report for 1 HLA-DRB1*0301 allele

Example: Promethease report for  1 HLA-DRB1*0301 allele

Genetic Genealogy

Genealogy testing matches testers with recent relatives. Matching is useful for traditional genealogy, parent searches, adoption searches, and informal paternity testing.

Maternal Matching

Because mitochondrial DNA (mtDNA) follows exclusively the direct maternal line, it if very good for proving that two people, male or female, share a common maternal ancestor. This can be essential evidence for genealogy.

Beyond this, it can also serve as a guide post when working with autosomal DNA matches. That is, when looking at your and an autosomal DNA match's five generation pedigree, also sharing mtDNA tells you that the match comes through the line of only one of your sixteen 2nd great grandparents.

For genealogy DNA testing, Family Tree DNA is the only company that offers both the testing level needed for genealogy, the mtGenome, and matching.

Paternal Matching

For genetic genealogy, Family Tree DNA is the only company that offers both high level Y-STR and Y-SNP matching.

Y-STRs

Y-SNPs

Autosomal Matching

X-chromosome Matching

Frequently Asked Questions

Why take a DNA test?

There are many reasons for DNA testing. They include medical, lifestyle, ethnic origins, paternity testing, adoption search, and genealogy.

Where can you take a DNA test?

There used to be only three major players in the genetic genealogy market. However, new options have emerged. These are the companies that are considered reputable by the expert mavens of direct to consumer (DTC) testing: Ancestry.com, Family Tree DNA, Living DNA, Insitome, myHeritage, and 23andMe.

What are the types of DNA?

There are four types of DNA that can be tested. They are autosomal DNA, X-chromosome DNA, Y-chromosome DNA, and mitochondrial DNA (mtDNA).

How much do DNA tests cost?

The price for DNA tests range from $59 to over a $1000.

Sources and Resources

Genetic Testing – Wikipedia

2017-11-28T08:20:15+00:00 January 26th, 2017|Categories: Compendium|Tags: , , , |