There are two types of DNA tests used for genealogical studies:

• Y-chromosome (Y-DNA): This test makes use of the Y-chromosome. Females have two X-chromosomes, while males have one X-chromosome and one Y-chromosome. It's the Y-chromosome that passes from father to son, making it invaluable in studying male-to-male lineage.

• Mitochondrial (mtDNA): The other method utilizes mitochondrial DNA (mtDNA), which is passed by a mother to both male and female offspring. A match between the mtDNA of a male potential relative and a female's mtDNA would mean the two have a common female ancestor. A male's mtDNA comes only from his mother and is not passed on to his offspring.

Since we're presently interested in tracing the van der Merwede (and variant) surname - which is usually passed from father to son - this study will use the Y-DNA method.

Even though the Y-DNA method will be used (and therefore only males will be tested), females are still encouraged to get involved. How? By letting someone else know about the study, or even ordering a test kit for that person.

There are three options for the Y-DNA test. The difference lies in how many markers are evaluated, which determines the usefulness of the results.

1. The first option looks at 12 markers on the Y-chromosome. Comparing those 12 markers to the same 12 markers of another male van der Merwede allows us to identify the likelihood the two subjects share a common ancestor. This likelihood is measured in generations back to the most recent common ancestor, or MRCA.

2. In a similar fashion, the second option looks at 37 markers. Comparing these 37 markers to the same 37 markers of another male van der Merwede gives a more exact estimate of the number of generations required to find the MRCA.

3. The third option increases the number of markers to 59. As you might expect, comparing 59 markers increases the likelihood that the participants share a common ancestor in the recent past.

Here's a chart that shows how increasing the number of markers can decrease the number of generations needed to get back to the MRCA..

As you can see, the 37- and 59-marker tests offer a much greater potential of establishing an MRCA in fewer generations.

For a more complete tutorial on genetics, DNA, etc., the Blair surname study has a fantastic tutorial called DNA 101. Thanks to John Blair for allowing us to link to his site.

How does the study work? >>