I’ve been doing genealogy for over 20 years now. Genetic genealogy has taken the world by storm only in the last few years. Millions of people have sent in DNA samples to the big companies. By matching with other living descendants of your ancestors, DNA has opened up a whole new era of exploration and collaboration. I may have info on an ancestral line my match doesn’t have or vice versa. When you start matching to an ancestral line where paperwork is sparse, such as Irish lines, DNA may be the only guiding light you have.

I am not a DNA expert, by any means, but I am learning a great deal. Ancestry uses a feature called Shared Matches. This means when you look at a match, say to Person A, it will show you matches who match both you and Person A above a certain threshold (20 centimorgans). This is helpful because if you don’t know where Person A fits in your tree, but you see he matches known Cousin 1, then you know he is probably on the same ancestral line as known Cousin 1.

As helpful as Shared Matches are, they are limited. For instance, I have several large groups that match to each other but not related to any known match. I don’t even know if they are on my mother or father’s side. With no family trees or responses from messages, how can I ever place them on my ancestral lines?

Other DNA sites employ a tool called a Chromosome Browser. This not only tells you how many centimorgans (the unit of measurement for DNA) and segments you share with that person, but exactly which segments on which chromosomes. People you match that are all from the same lineage will usually have some overlapping sections.

Here is an example of a chromosome browser:

Which can also be shown in chart form:

Once you have the chromosome information, you can use a tool called DNA Painter and “paint” them so you can see where they fall. As the segments align, you begin to understand which segments represent which ancestral couples. For example, this is a chromosome painted with 5 different matches from the same line overlapping:

Painting known matches, you can then take unknown matches and see if they overlap any of the known ones. If they do, this is an indication that they MIGHT be on that line. Why only “might”? Because each of our chromosomes have 2 sides—one from your dad, one from your mom. See below:

The chromosome browsers tell you which SEGMENTS you share with a match, but not which SIDE of the chromosome you match on. So if it seems to overlap on your dad’s side, it may be true. But it may also be on your mother’s side. However, it gives you a hint of where you might start looking.

Here’s one full profile from DNA Painter. This person’s profile is 28% complete.

Since most of my known matches are on Ancestry, I do not have chromosome information for most of them. I would be a lot further along in my chromosome mapping if I had them! Ancestry so far has insisted they will never provide a chromosome browser, so I am out of luck.

The more I learn about genetic genealogy, the more intrigued I become. The more tools we have, the deeper we can go into our origins.

Perhaps someday genetic genealogy will help me find the so-far-mythological DNA match to my mother’s Irish grandfather that will prove he was human and not an alien, figment, or leprechaun.