Direct-to-consumer genetic tests can open up new leads on who your ancestors were and where they lived. One of the ways home genetic tests do so is by looking at haplogroups, sets of genes inherited from your distant ancestors.
In general, you get half your DNA from your mother and half from your father, and the genes you get from each of your parents are a random mixture of the genes they got from their parents. This process of genetic mixing – recombination – is why genetics is basically a game of chance.
But some genes aren’t involved in recombination before being passed on to the next generation. A good example is the Y chromosome, which is what makes males male. Every man gets his Y chromosome from his father, who got it from his father, and so on. In other words, every man has the same Y chromosome as his father’s father’s father’s father.
There’s a twist, though. Rarely, small mistakes occur when the Y chromosome is being copied and passed on to the next generation – these mistakes are mutations. When one of these mistakes happens, the son ends up with a genetic variation, and he passes it on to his sons, who pass it on to their sons. After many generations, you end up with a bunch of men who all carry the same genetic variation on their Y chromosomes that links them to a common ancestor.
To put it another way, these men share a Y chromosome haplogroup. They have a common set of genes from a distant ancestor.
Because haplogroups are sets of genes that are always passed down from the same parent (either the mother or the father), each haplogroup provides information about either your paternal line (your father’s father’s father’s…) or your maternal line (your mother’s mother’s mother’s…).
Haplogroups that give information about the paternal line are on the Y chromosome, the chromosome that’s passed down from father to son. Since women don’t inherit the Y chromosome, the best way for them to find out about their paternal lines is to test a male relative who has the same paternal line (father, brother, father’s brother, etc.).
It’s also possible to learn about your maternal line by looking at another family of haplogroups, mitochondrial DNA (mtDNA) haplogroups. Mitochondrial DNA is a special kind of DNA located in a part of the cell called the mitochondrion. It is passed from mother to both male and female children, so it tells you about who your mother’s mother’s mother’s mother (etc.) was.
Every haplogroup is labeled with a combination of letters and numbers. When you do an online DNA test, you’ll discover your maternal haplogroup (and paternal haplogroup if you’re male), which you can then use to learn about your maternal line (and paternal line).
For example, you might do a genetic test and find that you have maternal haplogroup X2a. Well, what do those letters and numbers tell you? It turns out that haplogroup X2a is found mostly in North American Native Americans. In other words, discovering this is your haplogroup is a strong hint that you have North American Native American ancestry on your maternal line.
Online DNA testing services will often help you interpret what your haplogroup means – for example, by providing a map showing what parts of the world your haplogroup is most common in. Once you know the name of your haplogroup, it’s also easy to learn more using Google.
Knowing your haplogroup is useful because haplogroups are a simple yet powerful kind of information to have. Your maternal and paternal haplogroups are each just labeled with a few letters and numbers, but with those labels you can learn so much about who your ancestors were and where they came from!