The Big Y Test – Griswold DNA Project

By:  Becky Griswold

Family Tree DNA has a relatively new Y-DNA test called the Big Y test…and it’s a game changer!

The Y-DNA test that many Griswold Family Association members have taken is a Y-DNA STR test. STR stands for Short Tandem Repeat. STRs are mutations on the Y chromosome that are handed down from grandfather to father to son virtually unchanged. A Short Tandem Repeat occurs when the building blocks of DNA, bases called A, T, G, and C, (Adenine, Thymine, Guanine, and Cytosine) string together in a certain order and are then repeated several times on the Y Chromosome.

We use the STR test to determine if a male Griswold tester is a descendant of Edward or Michael Griswold. It has been a very useful tool to determine this. Edward descendants have unique marker values so that when a tester’s Y-DNA has these mutations we know immediately that they descend from Edward Griswold. If these mutations are absent from a tester’s Y-DNA, then we know he descends from Michael Griswold.

Unfortunately, that is about the extent of what the Y-DNA STR test can tell us. However, with FTDNA’s Big Y test, not only will we be able to definitively tell who descends from Edward and who descends from Michael, we can tell which son of Edward’s or Michael’s he descends from.

Here is how the Big Y test works. With Big Y you also get mutations. These mutations are called SNPs or Single Nucleotide Polymorphisms. The building blocks of DNA, A, T, G and C (remember those?) are paired up with each other to form a base pair on your DNA double helix. Every once in a while, one of the letters in the pair changes to another letter, i.e., a G becomes a C or an A becomes a T, etc. When this happens, it is called a Single Nucleotide Polymorphism or SNP.

These SNPs then pass down from grandfather to father to son, etc. just like the STR does. However, unlike STRs which can occur in any descendant at any time, a SNP will be present in ALL direct male descendants. Once we determine the SNP that we can attribute to Edward or Michael, all of their direct male descendants will also carry that same SNP. Then every 3 generations or so, a great-grandson might get a new SNP that will be unique to only HIS male descendants. Neither his father nor grandfather will have this new SNP, but his sons and grandsons will. It is this nature of the SNP that will allow us to use the Big Y test to know which Griswold branch each tester is from.

Right now, the Big Y test is pretty expensive. But the information it gives us is priceless. I am sure the price will come down as more and more people take the test. But for right now we can always take advantage of FTDNA’s sales. The next sale will be at the end of the year. Of course, you don’t have to wait for a sale. You can upgrade to Big Y at any time.

DNA, in general, is only useful when our results are compared to another tester’s results. It is the same for the Big Y test. If only one or two men upgrade, we are not going to learn much. But once we get enough testers from each of Edward’s and Michael’s lines who represent each of their sons, then we will get a DNA SNP signature for each of these branches. With each subsequent Big Y test upgrade, we will know immediately which line the tester belongs to because they will get that same SNP signature. If each Griswold man who has already taken the STR test would upgrade to the Big Y, we would have enough data to know that if a new Big Y tester came along, we could tell just by their Big Y SNP, without even looking at their lineage, which Griswold branch they were from.

The Griswold DNA Project currently has many Mysteries which we have been unable to solve using STR testing. We have quite a few testers in the project whose STR tests have placed them as a descendant of either Edward or Michael. However, there is a gap in their lineage that we can’t fill by research alone. Thanks to Coralee Griswold’s exemplary research, we have taken their lines back as far as we can. Due to missing or non-existent documentation, we cannot fill the gap that would connect them to Edward or Michael. Big Y would help us fill these gaps.

I am using the Edward/Michael group as an example, but the Big Y test will help all other Griswold groups as well.

If you would like to know if you should upgrade to the Big Y test, the answer is YES!

The Big Y test can potentially help us solve all of the mystery lineages we currently have. However, we need anyone who has taken a STR test and has a proven Griswold lineage to upgrade to Big Y so we have a SNP signature for each of these lines. Then, no matter if a tester has a gap in their lineage or not, a Big Y test will tell us immediately which Griswold branch they are on.

Once you upgrade to Big Y, that is it! Well…at least until the cost of Whole Genome Sequencing comes down!!!

If you would like to know more about the Big Y test, please email me at


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