DNA Basics: What DNA Testing
Can Do for You

Everyone has DNA. But most people don't understand the DNA basics.

While your DNA is different than mine, it is much like that of your parents and other people in your family tree. That makes DNA ideal for relationship testing of two presumed relatives.

The classic relationship test is a DNA paternity test, such as EasyDNA.

Comparing a child’s DNA with a suspected father can determine—without any doubt—if that man fathered the child.

Today, DNA can also confirm other relationships, like siblings, half siblings, grandparent and grandchild, and aunt/uncle with nephew/niece. The more distant the relationship the less DNA you have in common. But you can detect many distant cousins. Those are DNA basics.

DNA Basics: Testing Yourself

There are large and growing databases of people who have already taken the most popular tests. By testing yourself, you will learn who you match. Over time, you will see additional matches as more people get tested.

Combining family tree information from your matches with what the DNA says about your relationship is what leads to new discoveries in YOUR family tree. For example:

  • Genealogists are using DNA tests to get around their “brick walls” where the paper trail ends.
  • Adoptees are overcoming family secrets, sealed records and even outright lies to discover and reunite with their biological families.
  • People curious about their ethnic ancestry are learning what parts of the world their ancestors came from.
  • Adults who discover or suspect that the man who raised them was not their biological father are identifying previously unknown fathers.
  • Children of sperm and egg donors are testing their DNA to find biological parents and siblings.

Testing additional family members from different branches of your family tree can provide even more information when you see which matches you have in common or not in common.

DNA Basics: How Do I Get Tested?

It’s easy. You order a test from the company’s website. They ship a home test kit to your address. You collect a sample of your DNA and send it back. 

They analyze your DNA and compare it to every other person who has taken the same test. They notify you by email when your results are ready. Then you log into your private, password protected account to see your results.

Collecting your DNA sample is easy and painless with my recommended DNA testing companies.

AncestryDNA and 23andMe use a “spit kit” where you simply collect some saliva in a tube.

Family Tree DNA, MyHeritage DNA, and Living DNA use test kits that include swabs for lightly scraping cells from inside your cheeks. Either method is generally effective.

Subjects who are very young or very old may have difficulty producing a lot of saliva or spitting into a tube. For them the cheek swabs will be easier to use.

DNA BASICS TIP: A mortician can use cheek swabs to collect DNA from the recently deceased, though I recommend you don’t wait that long.

How DNA Passes Down the Family Tree

Everyone has a biological family tree, even if you’re unaware of anyone but yourself. You have two parents, four grandparents, eight great-grandparents etc. You need to understand three major types of DNA and how each type passes down the family tree.

1. Autosomal DNA (abbreviated atDNA) passes down from ALL your ancestors. At each conception, a child receives approximately 50% of this DNA from each parent. But which 50% you get is random. You will probably not inherit equal amounts from each grandparent and your siblings will likely get a different mix.

Your matches can reflect common ancestors from any branch of your family tree. Yet after five generations or so, the amount of DNA you have from any one ancestor may or may not be detectable. In terms of your family tree, think of autosomal DNA testing as having a broad but relatively shallow reach.

See Understanding Autosomal DNA to Learn More.

There are multiple testing companies offering autosomal DNA tests. For a brief overview of their relative strengths see the Autosomal DNA Comparison page.

Many people take autosomal DNA tests for the ethnicity reports. To learn more about that see Understanding DNA Ethnicity Testing.

Autosomal DNA tests are a great way to determine how two people are related. See this page on Understanding DNA Relationships.

Today there are many powerful tools available to help you figure out HOW your genetic matches are related to you. Some can be used within your testing company accounts. Others are available from third parties. For a brief overview of the most popular ones, see Genetic Genealogy Tools.

2. Y-DNA focuses on the Y chromosome, which men inherit from their father, who got it from his father etc. Y-DNA testing covers the direct paternal line and only men can be tested. Yet many women participate by testing a suitable male relative.

Since the Y chromosome passes on mostly unchanged—and surnames usually pass down the same paternal line—Y-DNA testing can help trace your PATERNAL ancestry.

Your direct paternal line is just a tiny part of your overall ancestry. Yet Y-DNA testing can uncover matches from common ancestors who lived hundreds of years ago. Think of Y-DNA testing as a narrow but deep test of your family tree.

See Understanding Y-DNA to Learn More

3. Mitochondrial DNA (abbreviated mtDNA) is a type of DNA that mothers pass on to all their children. Both men and women have mtDNA but only women pass it on.

An mtDNA test can help trace your MATERNAL ancestry back hundreds of years. Like Y-DNA testing, it’s a narrow but deep test of your family tree.

See Understanding Mitochondrial DNA

Read My DNA Testing Strategy

People have many different goals for DNA testing. For an overview of my general DNA basics testing strategy see DNA Test Strategy.

If you are an adoptee or are otherwise looking for biological relatives, see my step-by-step strategy for Tracing Birth Parents.

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Like many bloggers in this field, I depend on income from affiliate links to support my writing about DNA testing. This allows me to develop valuable free content and answer thousands of DNA questions a year.

If you plan to order any DNA test mentioned on this site, please click on my link to order it directly from the testing company. You won’t pay any more but I will earn a small commission.

I refuse to join affiliate programs for any product or service that I can not wholeheartedly recommend.



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