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What different types of DNA test can you have?

1 The male line DNA test (Y-STR test)

In this first article, we look at the Y-STR test, a DNA test that can be used on men only. Women wanting to find where they fit into one of the genetic surnames studies need to persuade a close male relative (brother, father) to take the test and submit their DNA. Why? Read on...

DNA tests and the Y chromosome

All human beings have 46 chromosomes, 23 pairs. Chromosomes are bundles of DNA that look a bit like starfish with four legs. Chromosomes halves (indicated by label 1 in the diagram below) attached at a single point, the centromere (label 2). The bits on either side of the centromere are different lengths - called short arms (label 3) and long arms (label 4).

In women, each pair of chromosomes is a good matched pair but only 22 pairs of a man's chromosomes are evenly sized. One pair of chromosomes, the sex chromosomes, are different in men. Men have and X and a Y chromosome whereas women have two X chomosomes.

The Y chromosome is smaller than all of the others and contains a lot of non-coding, 'junk' DNA. This has a lot of repeats of DNA code in it and this is very useful for DNA tests. These repeated sequences are passed down from father to son, just as surnames in Europe have been for the last six to eight hundred years.

For family history, testing the Y chromosome can be useful to work out relationships along the paternal line and can show if men with the same surname are closely related or not.

What use is the Y-STR test for family history?

The Y-STR test identifies the number of repeated sequences at key spots in the DNA on the Y chromosome. These areas can be compared between different men and it is possible to estimate whether they shared an ancestor two, five, eleven or more generations back. Such a test can suggest how closely related two men with the same surname may be.

It is therefore a useful test in one-name studies that make use of genetics such as the Sykes study. If you are just starting out in family history, it is probably not worth having a test. In the future, as more DNA samples and sequences are added to databases, it might become possible to join a one-name study and, just through your DNA test results, be able to find out which branch of that particular family tree you fit into.

This is not possible for most surnames yet, but some are moving rapidly towards it.

Find out more about genetic surname studies by following these links:

The Sykes surname genetic study

The Williams surname genetic study

The Harris surname genetic study

The Lewis surname project

The Ball surname project (Y-chromosome testing)

A Smith surname genetic study (one of several)

Another Smith project

The Johnson surname genetic study

The Jones surname genetic study

The Brown surname genetic study