DNA is made up of four chemicals that we abbreviate as A, C, T, and G. DNA has two strands, with one chemical on one strand pairing with a complementary chemical on the other strand. We call these pairs nucleotides. Sometimes a small copy error occurs where one chemical is substituted for another on the DNA strand. For example, an A can be copied as a T or a C copied as a G. When this occurs on a single nucleotide, we call it a Single Nucleotide Polymorphism or a SNP (pronounced snip).
These changes are usually rare, and many generations can pass without a SNP occurring. This means that SNPs that occur in a specific lineage are unique and seldom change back. Most SNPs are ancient. They occurred thousands or tens of thousands of years ago. Some are more recent, and as science evolves we are discovering some that occurred in just the past few generations. As the science of genetic testing has advanced and the size of the database has grown, this time frame is coming closer and closer to the present day.
Your Ancestral Origins
Our Y-DNA marks the path from our direct paternal ancestors in Africa to their locations in historic times. Your ancestors carried their Y-DNA line on their travels. The current geography of your line shows the path of this journey. This information comes from scientists who study the history of populations across geography and time using Y-DNA. They use both the frequencies of each branch in modern populations and samples from ancient burial sites. With these, they are able to tell us much about the story for each branch. This traces back hundreds, thousands, or even tens of thousands of years. Your branch on the tree tells you where your paternal ancestors are present today and about their likely migration paths. This is your Y-DNA haplogroup.
Applications to Genealogy
When a SNP occurs, this change is passed down to future generations. Y-SNP testing focuses on nucleotide changes found on the Y chromosome. Only males have the Y chromosome, so these changes are carried exclusively on the male (direct paternal) line.
The Big Y test changed the paradigm of Y-SNP testing. Before the Big Y, SNP testing was primarily useful before the advent of surnames; but today, SNPs are useful in determining genetic lines of both closely and distantly related men. SNP markers mutate at a much slower rate than STRs, which makes them more stable for determining relationships. But you need to test millions of locations to find the relevant markers, which is exactly what the Big Y test does.
Choosing the Right Test
While the most expensive option for Y-SNP testing, the Big Y-700 test is the most comprehensive in a variety of ways. As the haplotree grows, SNPs that have been tested in a Big Y-700 test will gradually be placed on the tree, furthering your own research. Individual SNPs can quickly add up in price and SNP packs may potentially leave you with a branch that is hundreds or thousands of years old. Click here to learn more about the Big Y test.
The many testing options available can be overwhelming, but the good news is that FamilyTreeDNA offers a wide variety of Group Projects to help you decide which test will be the best for your particular research goals. These projects are run by volunteer administrators who specialize in the haplogroup, surname, or geographical region that you may be researching. Different projects have different requirements and different areas of focus. You can explore our Group Projects here to see if you find one that fits your needs. If one sparks your interest, you may try reaching out to the administrator to help you in your genetic genealogy quest.
Y-SNP Test Options
There are three main types of SNP testing: BigY-700, SNP packs, and individual SNPs.
The Big Y-700 Test is an exploratory test that explores a SNP-rich region of the Y chromosome. It does not search for specific SNPs. Instead, it covers this area with a 70x read and reports all the SNPs that are found with a high confidence rate. This means you will receive results for hundreds or thousands of known SNPs as well as new SNPs that have not yet been discovered or added to the Y Chromosome tree of mankind. As more and more test takers uncover these same SNPs, we are able to find their placement on the tree and continually update your own placement.
In addition to SNPs, the Big Y-700 includes the 111 STRs found in the Y-111 test and provides your STR matches as well. It will also provide a minimum of 589 additional STRs for a total of 700+.
Those who have taken a Y-STR test such as a Y-37 or Y-111 receive a haplogroup prediction that is generally a low-resolution general haplogroup dating thousands or even tens of thousands of years ago. SNP Packs are branch-specific tests that are designed to help refine this ancient haplogroup to a more recent branch. There are many SNP packs available, and we recommend joining a haplogroup or surname project and asking the Group Administrator of that group which test is right for you. They can help analyze your Y-STR test results to see which branch you should focus on.
If you have taken a Big Y-700 or SNP Panel test and wish to further refine your haplogroup or to test a hypothesis, you can order any SNP on the haplotree as an individual order. We highly recommend discussing this option with a Group Administrator before ordering.