When you open your DNA results for the first time, you’re often met with a wall of technical terms. It can feel like you need a degree in genetics just to view your results!
To help you move from confusion to connection, I’ve put together this guide to the most common terms you’ll encounter on your journey to finding your “Forever Dear” ancestors.
1. The Basics: What are we looking at?
- Autosomal DNA: The DNA you inherit from both parents. This is what the “Big Four” tests (Ancestry, MyHeritage, etc.) use to find your cousins across all branches of your tree.
- Centimorgan (cM): This is the unit of measurement used to calculate how much DNA you share with someone. The more cMs you share, the more closely you are related.
- Segment: A specific block of DNA that you share with a match. If you share several long segments, it’s a strong sign of a recent common ancestor.
2. Your Ethnicity and Origins
- Ethnicity Estimate: A breakdown of where your ancestors likely lived hundreds or thousands of years ago. It’s important to remember this is an estimate, not an exact science!
- Genetic Community / Genetic Group: These are more specific than broad ethnicity estimates. They use DNA matching to link you to a specific location or group—for example, East Cork or Mid-Meath Settlers. This is often the most accurate part of your results for Irish research.
3. Understanding Your Matches
- MRCA (Most Recent Common Ancestor(s)): This is the person (or couple) that both you and your DNA match are descended from.
- Shared Matches: A list of people who match both you and another person. This is the best way to figure out which side of the family a match belongs to.
- Endogamy: This occurs when a group of people stays within a small community or island for many generations. It can make matches appear more closely related than they actually are because you share DNA from multiple common ancestors. This is common in many rural Irish communities!
4. Advanced Specialist Terms
- Triangulation: The process of finding two matches who also match each other. When all three of you match on the same segment of DNA, you can be fairly certain you all share a specific MRCA.
- Phasing: The process of separating your DNA results into maternal and paternal sides. Some testing sites (Ancestry, MyHeritage, etc.) do this automatically, helping you see which matches come from which parent.
My Top Tip for Beginners
Don’t let the technical terms put you off! If you only learn one term today, make it cM (Centimorgans). Once you understand that a higher cM count means a closer cousin, the rest of the puzzle starts to fall into place.