Big Y-700 DNA Test: When To Use It

Family Tree DNA’s Big Y-700 test can help you distinguish fine shades of relationship on the paternal side of your family tree.

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In January 2019, Family Tree DNA released the latest-and-greatest version of its Big Y DNA test: the Big Y-700. As the name suggests, this is a Y-chromosome DNA test, useful for sorting out genealogical relationships on your paternal side (father’s father’s father’s father, etc.). A regular 37 or 67 marker DNA test can help you determine whether two men with the same or similar surname are related, or help you find a surname for an unknown male line.

The Big Y-700 test just takes those same principles to the next level. It is especially good at helping you determine HOW you might be related to someone that the regular YDNA test says you are related to. More on that later.

What is Big Y-700?

Big Y-700 explores two different kinds of genetic markers: STRs for more recent DNA connections and SNPs for more distant connections.

STRs are short repeating sections of DNA that can have a lot of variability between generations, making them good for identifying genetic relationships within the past 10 generations or so. So while the 67 marker YDNA test looks at 67 STRs, the Big Y-700 test looks at 700 STRs (hence the name of the test!).

SNPs are single changes in the DNA, and lots of times they change SUPER slowly (like, over thousands of years), so they point to your paternal ancestors’ ancient populations and migrations. However, there are lots of SNPs that may have changed in more recent generations, but just haven’t been well documented yet.

The Big Y test is helping us build a database of those newer SNPs. It does that by finding unique YDNA SNPs specific to your paternal line for the time frame of about 10 - 20 generations back—effectively filling part of the genetic gap between what STRs can reach, and the more commonly reported deep ancestral SNP markers that tell you about ancient migrations.

When should you use Big Y-700?


The Big Y-700 test is most useful when you have solid paper trails for a paternal line and traditional YDNA testing with good matches going back at least 8 generations. This test can help you make genetic connections in the shadowy, pre-genealogical timeframe most people encounter at 10-20 generations, where records often don’t survive, surnames didn’t exist, and autosomal testing isn’t helpful.


The “700” part of Big Y-700 can help make greater distinctions between lines you know are related: for example, help you distinguish your ancestor from among his three brothers. Lower-marker YDNA testing (even at the 111-level marker level) may not be able to answer that question for you. However, it will only be helpful if you can get you matches to take the test also. Having just your own Big Y results won’t be very insightful.

If I took the original Big Y test, do I need to upgrade?

Well, that depends. According to the white paper published by FTDNA, “Big Y-700 customers can expect to receive 40% more STRs and 50% more high-quality SNPs than they did with Big Y.” That means more data to help determine family relationships.


Family Tree DNA has the world’s largest YDNA database. Whether you’re ready for Big-Y 700 or starting at a lower level, Family Tree DNA is the place to take your YDNA test.

Whatever level your YDNA testing, you may have questions. My YDNA Quick Reference Guide has easy-to-understand answers! It’s an inexpensive way to ensure you get the MOST out of your investment in YDNA testing.


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