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.
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.
Please take the highest yDNA marker test you can afford. The Big Y test will give the best results. If you can't afford one of the higher marker tests take a lower marker test. You might be asked to take a specific marker on a later date.
1. The Big y-700
If you test one of the following tests you might be asked to test for a specific marker at a later.
2. Y-111 tests 111 markers
4. Y-37 tests 37