DNA was first identified in the 1860s by chemist Friedrich Miescher, but it wasn’t until the 1950s that James Watson and Frances Crick uncovered its iconic double-helix structure and paved the way for all the DNA advances that we have today. We are now at a point in history where anyone can send their DNA off for analysis and uncover a whole host of interesting information about their ancestors. Still, you might be wondering just how far back in history you can go. Let’s take a look.
Why is DNA called the blueprint of life?
All living organisms rely on protein to be able to sustain life. Protein is used to create every part of your body, from cells to tissues and organs. But this protein has to be told what it needs to form itself into, and this is where DNA comes in. DNA is a macromolecule that stores all of the information needed to create every part of your body from different types and combinations of proteins. In other words, it is the blueprint used to create you and to keep you alive.
This is why it is called the blueprint of life and, although it was discovered extremely recently in terms of human history, scientific advancements in DNA analysis are already being felt in all areas of life, from healthcare all the way to crime-solving.
What are the different types of DNA? What can we learn from them?
When we are talking about DNA, we often aren’t talking about it in its pure form because that isn’t how the body uses it, nor is it how it is inherited between generations. Instead, DNA is chunked into segments called genes, and it is each of these segments that code for a specific protein that can then be used to build a part of your body. The genetic code, which is made up of four bases (A, T, C, and G), determines the number of amino acids used to create the protein and the order that they should go in.
Chromosomes are structures found within the nucleus of each of your cells, and they contain your genes. Humans have 46 chromosomes in total, arranged in 23 pairs. You inherit one of each pair from each of your parents, who each inherited one of each pair from their parents. 22 of the 23 pairs are known as autosomal, and they are the same for both men and women, whereas the 23rd pair are your sex chromosomes, and they determine your biological sex.
Autosomes are chromosomes that are the same in both males and females, and everyone has 22 pairs of these. In terms of ancestry DNA testing, autosomal DNA can be used to trace the autosomal segment found in your DNA. This is achieved by comparing your autosomal DNA to everyone else in the DNA database. Doing so can link you to people you are related to and give an estimated percentage of your ethnic ancestry.
The process is complicated slightly, however, by the fact that your autosomal DNA goes through recombination. This is when pieces of DNA are broken and then recombined, and it can result in the mixing of paternal and maternal DNA, meaning that you have different combinations of genes than your parents.
The evolutionary benefit of recombination is that it enhances genetic diversity, which can mean a less likely chance of inheriting certain genetic diseases and allows you to cope with environmental pressures and new diseases more easily.
Mitochondrial DNA (mt-DNA) is passed onto offspring by their mother. Mitochondria are structures found within the body’s cells that convert energy into a form that the cell can use (ATP). Mitochondria have DNA that is separate from the rest of the body’s DNA, and it contains 37 genes in total.
Although much smaller in number than autosomal DNA, Mitochondrial DNA can also significantly affect the way your body functions. Because mitochondria are responsible for converting energy at a cell level, problems with mitochondrial DNA tend to be related to organs that require a lot of energy, such as the heart, muscles, and brain.
Since everyone inherits their mitochondrial DNA from their mother, both males and females can see their results related to mt-DNA in any ancestry results that they take. In addition, because mt-DNA is inherited directly from mother to child and doesn’t intermix with the rest of the body’s DNA, there is very little recombination.
Any that does occur happens at a much slower rate. Because of this, mt-DNA can be used to trace an individual’s lineage to many more generations. This can be done by relating your mt-DNA to its maternal haplogroup, a branch (or group of related branches) on the human genetic family tree.
Y-DNA is DNA that comes from the Y chromosome, one of the sex chromosomes. Everyone has one pair of sex chromosomes, with one inherited from each parent, and the combination you have will determine your biological sex. For example, females have two X chromosomes (one from their father and one from their mother), and males have one X chromosome inherited from their mother and one Y chromosome inherited from their father.
Some individuals will have different combinations of sex chromosomes, known as sex chromosome disorders. They may inherit three sex chromosomes (e.g., XXY or XXX), or they may be female with XY chromosomes. You will likely already know if you have one of these disorders.
Because only biological males have a Y chromosome, they are the only ones who will be able to trace their Y-DNA heritage (although females can use their male relatives’ DNA if they want to trace their paternal lineage).
While Y-DNA isn’t separate from the rest of your DNA in the same way that mt-DNA is, 95% of it is immune from recombination, so it can also be used to trace your lineage much further back than autosomal DNA. And it can uncover your paternal haplogroup.
How many generations should autosomal DNA test results attach to?
We’ve seen that mt-DNA and Y-DNA can trace your maternal and paternal haplogroups, respectively, and these can go back to a thousand or more years for both. Still, they won’t give you much detailed information about your specific ancestors (only around 1%). On the other hand, Autosomal DNA can give you detailed information about your genealogical history, although it doesn’t go back as far.
This is because it looks at a much greater variety of shared DNA that can then be compared with samples in the DNA database. So if you are interested in uncovering your family tree, it will be autosomal DNA that will achieve this. In contrast, mt-DNA and Y-DNA can be more helpful in examining your ancestral maternal and paternal ethnic and geographic history.
Most estimates say that you will be able to trace your ancestry up to 5-8 generations (up to approximately 200 years) using autosomal DNA. But, as we have discussed, this is only an estimate because DNA can be recombined in different ways, which may mean that you miss certain branches of your family tree.
And, because you only inherit 50% of your DNA from each parent, your DNA won’t show genetic information that didn’t get passed on to you. So, for a more detailed pattern of DNA inheritance, it can be an excellent idea for everyone in your family who shares your DNA to get tested.
How much of your genome do you inherit from a particular ancestor?
Let’s take a closer look at why we are so limited with how far we can go back using autosomal DNA by examining what percentage of DNA we can expect to inherit from each ancestor.
- Parent – 50%
- Grandparent – 25%
- Great grandparent – 12.5%
- Great great grandparent – 6.25%
- 3rd great grandparent – 3.125%
- 4th great grandparent – 1.56%
- 5th great grandparent – 0.78%
- 6th great grandparent – 0.39%
- 7th great grandparent – 0.20%
- 8th great grandparent – 0.10%
Remember that apart from the percentage you inherit from your parent, the percentages for all the other generations are estimates. On average, for example, you will inherit 12.5% of your autosomal DNA from your great-grandparent, but in reality, this percentage can be higher or lower. This is, of course, complicated even further by recombination, which can leave you with a different combination of inherited genes than your parents.
Once you get as far back as your 8th great grandparent (or even before), the average percentage is so tiny that there is a chance that you won’t inherit any of their DNA in reality. And this is where the thread that links you to that branch of your ancestry ends. In addition to this, autosomal DNA ancestry testing relies on databases of DNA samples.
This can be from other users who have sent in their DNA or from reference samples known to have strong ancestral roots to specific geographical areas. Because you are comparing your DNA sample to a small subset of other DNA samples, there is a greater chance that genetic connections may be missed when you go further back in the generations (where you will share a smaller percentage of your DNA).
When you get your autosomal DNA analyzed, you will likely receive an estimate of your ethnic heritage and the geographical location of your ancestors that goes back much further than eight generations. This part of your results uses estimation techniques to compare your DNA to the known migration works of ancestors that share your DNA.
These results can be fascinating, but they are an estimation and may miss some of your ancestries. You may even find that your results differ from your sibling’s just because you inherited different DNA that came from your ancestors than they did.
Are all ancestry DNA tests created equal?
With ancestry DNA tests becoming ever more popular, there is now a wide range of companies to choose from when it comes to getting your DNA tested. Many of them will offer similar types of testing, but different techniques can be used. You might be wondering whether you can expect identical results if you get your DNA tested by each of the different companies or whether these results will differ depending on the company you use. Let’s look at some of the most popular DNA testing companies to see what they offer in terms of ancestry DNA tests.
Ancestry DNA is one of the most well-established companies that test ancestral DNA. However, they are vocal about only conducting autosomal DNA testing because it gives the fullest picture of your most recent ancestry. They do not conduct Y-DNA or mt-DNA testing.
They use microarray-based testing to survey over 700,000 locations across your entire genome. This autosomal DNA testing looks for single nucleotide polymorphisms (SNPs) as DNA markers. These are places on the genome where people’s DNA tends to differ.
These markers are then used in two ways. First, they are compared against a reference list of DNA samples. These come from people who have deep ancestral roots in specific geographic areas. By comparing your DNA to these samples, you will receive an estimate of your geographic, ethnic heritage.
Second, your DNA sample can be compared against all other users in the Ancestry DNA database. This can be used as genealogy research to pinpoint your family tree and find long-lost relatives.
23andMe is perhaps more well known for their health-related DNA testing, but they also offer an ancestral DNA option. Like Ancestry DNA, their autosomal DNA testing compares your SNPs to a database of people who have deep ancestral roots in some geographical regions. And they also use public reference databases, such as the Human Genome Diversity Project, Hap Map, and the 1,000 Genome Project.
23andMe are open about the issues with these ethnic estimates. For example, the samples used are historically biased towards people of European descent, making it more challenging to pick up on ethnic heritage from other geographical areas. Still, they are currently expanding their database to make it more inclusive.
Unlike Ancestry DNA, however, included in your 23andMe report will be your Y-DNA and your mt-DNA results. This can help to give you an even fuller picture of your genetic heritage, and it is included as standard.
Family Tree DNA
The Family Tree DNA autosomal DNA test works the same way as Ancestry DNA and 23andMe. They use microarray-based testing that examines 69,000 pairs of data points to extract your SNPs and compare them to their database. In addition, their Family Finder database allows you to connect to relatives who share segments of your DNA, and you will also receive an estimate of your geographical ancestry.
Family Tree DNA offers both Y-DNA and mt-DNA testing as well as autosomal, but they have to be ordered separately.
The DNA testing from Nebula Genomics works differently from the microarray testing offered by the previous three companies. Ancestry DNA, 23andME, and Family Tree DNA all use microarray technology to analyze your DNA. This uses predetermined segments of DNA that are already known to be SNPs (and therefore relevant to ancestry testing) as markers against which your DNA is tested.
On the other hand, Nebula Genomics uses whole-genome sequencing for its DNA analysis. Rather than analyzing only these predetermined segments of DNA that contain SNPs, whole-genome sequencing analyzes our entire genome, which contains between 20,000 and 25,000 genes.
Through whole-genome sequencing, the entire blueprint of your DNA is revealed. In and of itself, this can be fascinating, but does it impact the accuracy of ancestry DNA testing?
This type of DNA sequencing can be superior to microarray testing in a health setting because it can uncover rare genetic mutations that could impact your health. However, the benefits of whole-genome sequencing versus microarray are less noticeable when tracing your ancestry.
One of the most significant selling points for Nebula Genomics in terms of ancestry is that they decode the entirety of your Y chromosome and mitochondrial DNA and your autosomal DNA, which allows you to get the fullest picture of your genetic ancestry.
To wrap up
Finding out about your genetic ancestry using DNA testing can be illuminating, thought-provoking, and can answer any questions about who you are. In addition, understanding how this type of testing is conducted and what the different types of DNA testing can reveal to you can help you make a more informed decision about the type of testing that will work for you.
Finally, it can shed greater light on the meaning of your results. And as more advances are made and the DNA databases are expanded and updated, we will all hopefully be able to find out about our past in even greater detail.