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Can I use a DNA test to research my family history?

Some people do have the idea that if they have a DNA test, their results can be put into a computer somewhere, and they will then be able to print out a plot of their entire family tree.

This, as you have probably guessed, is not anywhere near possible. However, DNA technology and DNA tests are being used in genealogy and the information they provide can be very interesting and useful.

In a series of articles, Family Tree Folk looks at the role of DNA technology in genealogy today, and explores a few possibilities of how it might be used in the future. You might think DNA genealogy is not for you - but finding out more about it might suggest some interesting possibilities. 

Scroll down to find out more...

What is DNA?

DNA is an abbreviation for deoxyribonucleic acid. This is a complex molecule found in the nucleus of most living cells in the body. DNA holds the information that tells each cell what to do – which proteins to make, which shape to take, where in the body to go, what job to do.

The DNA molecule is a double helix and its structure allows it to act as a giant secret code that carries information.

The strands of DNA that form the double helix contain four main components, called bases, that can be arranged in any order. They act a bit like a four-letter alphabet made of the letters A, C, T and G.

  • A is for Adenine,
  • C is for Cytosine,
  • T is for Thymine,
  • G is for Guanine.

In the helix, the adenine always meets up with thymine across the gap, and cytosine always pairs up with guanine to make the bars that hold the two backbone rails of the helix together.

The entire DNA in a human cell – called the human genome – has three billion of these base pairs. The lengths of DNA contain the base pairs in many different sequences – this is what carries the coded information.

Some parts of the code spell out instructions that can be understood by the cell – these stretches are called genes. In between the genes are sections of DNA that help control the genes, or just separate them from each other – often called non-coding DNA.


What is DNA for?

Each cell of the body has exactly the same DNA but not all cells make use of all of it all of the time. The position of the cell in the body causes some genes to be used – they are switched on. Other genes, the ones not required by that cell stay unused – they are switched off.

The information in DNA is passed down from generation to generation, in the DNA that goes into the egg and sperm that join together to become form a fertilised egg, an embryo, and eventually a newborn baby. Each one of us shares DNA from our natural father and mother – we aren’t identical to either of them – but we have a lot of DNA sequences in common.


How does DNA differ between people?

The DNA of every human being is very similar – much more similar than to any other animal, even the closely related chimpanzee.

The DNA does differ a little bit between different people though – this is the result of mutations in the DNA – tiny changes to the code that accumulate over time. These differences are very important because they can be used to tell how closely related people are.

The two most closely related people, a pair of twins, both have identical DNA. Two brothers have very, very similar DNA. Two cousins have similar DNA, but there is not quite some much in common. Two unrelated friends have significant differences in the parts of their DNA. This is the key to understanding why DNA technology can be useful in family history.

How does DNA technology help us understand family history?

If two men with the same surname have a DNA test, it is possible to look at the results and gain a big clue as to whether they are closely related or not. This sort of study is quite common already. For example, there is a large DNA study concentrating on the surname Sykes, that is trying to establish if all men with the surname Sykes in the UK are related. Of course, this method can only be used for the male line of ancestors – women change their surname when they marry and have done since surnames became established. There are ways in which women can follow their female ancestry using DNA technology - more about that in the article on different type of DNA test.

The other thing that DNA test results are useful for is determining where in the country, or in the world, that your direct ancestors came from. There are DNA sequences that have originated in Africa, Asia, Europe at so on, from many generations ago, that can still be detected in our DNA today. By looking at which patterns we have, DNA experts can suggest whether our ancestors were European, and perhaps which part of Europe they came from.

Find out more in the follow-up articles:

What is the Y DNA test and what does it tell us about family history?

What is mtDNA testing and what can that tell us about genealogy?

Who were seven daughters of Eve?

What family history studies are using DNA technology?

How is DNA testing being used in Scotland?

How is DNA testing telling us information about ancient Egypt?

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