Recently I received a question specifically about Y-DNA.
Ancestry. com's DNA test, 23andMe, MyHeritage, and LivingDNA/Findmypast, all offer one type of DNA test you can buy. The scientific term for that test is an autosomal DNA test. They all have different features and ways they look at that DNA (like 23andMe looking at it for health information). However, they are all the same kind of test, testing the same kind of DNA.
Years ago when I started taking DNA tests the only big company in the business was Family Tree DNA. They were the first to offer the autosomal test, which they now market as the Family Finder test. I remember taking it from them before the others released.
Prior to that, they offered more focused tests that remain useful: Y-DNA, and mtDNA. They also offer some more niche tests like X-DNA, BigY, or specific markers. None of the other big genetic genealogy companies offer any of these. Some like 23andMe will tell you your Y-DNA haplogroup if you are a male as part of their testing, but they do not look at the Y-DNA in the helpful detail that Family Tree DNA can.
There was an old rumor going around that only males could do DNA tests. That rumor is based on the Y-DNA test. Y-DNA is for the male line only and only males inherit any Y-DNA at all. Female=XX. Male=XY. Don't worry if you do not get those letters, but just know only males have Y-DNA. The main value of it over the general (autosomal) DNA test everyone else sells is that Y-DNA is strictly on the straight male line so that it remains largely unchanged for many generations and focuses on one line. Autosomal tests are awesome at finding close family as distant as 4th cousins with very good accuracy. Relatives more distant have an increasing chance of not appearing as cousin matches because you may possibly not share enough DNA. To put it simply if you begin with yourself having 50% mom and 50% dad, then your kids only have 25% of each grandparent, and so on. So several generations down you only get such a small amount of DNA from an ancestor that autosomal testing gives the clearest results for recent family. Y-DNA remains largely unchanged for many more generations, so two solid Y-DNA matches can estimate a relationship many, many generations earlier. Sadly it can only be done on the male line.
If you have a specific issue like proving two Smith families have the same male Smith ancestor then having descendants from both lines test could prove it for you or disprove it. If you had your brother Mr. Smith test and had another Mr. Smith person test--or people you do not know randomly test someday and appear as matches--then you can determine those two lines have the same paternal ancestor if the match is strong enough. Sometimes genealogists use this to prove their Smith line had the same common ancestor as a well documented Smith line, even if they could not document their line that well with paper records. You often get a lot of Y-DNA matches that are not very strong and those matches mean little, except perhaps that most of them come from the same region of the world and have a prehistoric common ancestor. To take a match seriously within meaningfully recent history you typically want to match almost exactly on 30+ Y-DNA points. You may be able to see who you match at 12 or 25 points, but these matches mean much less.
So the unfortunate truth is that Y-DNA does little practically for a genealogist unless they have a second person test that they can compare too (or someone randomly tested who appears as a match).
That being said, you can also loosely determine a region of origin from Y-DNA too without any close matches. For example, I had my uncle Mr. Schilling tested (a German surname) and the majority of his matches had Irish/Scottish surnames. This scientifically supported a hypothesis I had previously developed that his great grandfather was the biological son of a man surnamed Callaham(?) and raised by a Schilling family whose name he took. In this case the Y-DNA provided useful evidence of something without even needing to have a close match.
In summary, Y-DNA can be a powerful tool, though it is generally only worth doing if you understand what it will do for you and need to solve a problem like what I discussed above.
mtDNA is similar. It passes through women, opposite of Y-DNA. Think of your tree like a triangle starting with you as the tiny point like this <. The top line is what Y-DNA tracks and the bottom like is what mtDNA tracks. It tends to be used less often for genealogical applications, but you could use it to prove or disprove a person's descent from the same direct maternal woman. It would have to be the direct maternal ancestor of both parties though (not on a different line). Males can do this as well as females because they do get the DNA from their moms, but they do not pass it down, so if their kids test the DNA that shows up will be the mom's DNA. There was news going around lately that challenges this, but last I checked a well known genetic genealogist had said that the news does not change how this works. The other tests are even less useful so I wont discuss them right here right now (X-DNA, etc.).
The current holiday sale prices for these tests are as follows:
Y-DNA: $99
Family Finder (autosomal): $49
mtDNA: $139
If you do decide to buy please go to the website using my affiliate link so that I will make 5% from your purchase. It is not much, but it motivates me to take the extra time to share this extra knowledge. You can also have your friends or family members go to the site through my link if they intend to buy, and this article was helpful.
I would love to talk with you more about these tests in the comments.
One resource I love to learn more about these tests is their own learning center. It explains the results you get and how to determine how many generations apart you may be from a Y-DNA match on your list.
FTDNA Learning Center – Paternal Lineages Tests
You can also access that page of the site directly through this custom link to ensure that if you end up purchasing a kit it will count for me too, but this way you can start on this help page and read all about it.
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