With the rise of simple DNA testing, more and more people are starting to understand the basic concepts of genetics. Particularly, people are learning how complex genetic inheritance is. We inherit from both our parents but in different ways. We’re also more “related” to one parent than another, but express more genes from the other parent.
The best DNA test will give you the opportunity to look into your maternal heritage as well as your paternal heritage. One looks only into the female ancestors of your mother, the other into the male ancestors of your father.
You should also be able to look into your ethnic heritage, but for now, let’s try to understand how genetics are passed down differently through women than through men.
A DNA test that uses mitochondrial DNA (mtDNA) will give you insight into your mother’s heritage. A Y-DNA test looks into the source of your Y chromosomes – your father.
The difference
Everyone inherits mitochondrial chromosomes from their mothers, men or women. But only women pass them down. This makes it so that technically we’re all “more related” to our mothers – we have more of their genetics. However, males generally have the upper hand when it comes to which genes are expressed. It’s confusing, as it should be, since most of us have a high school understanding of biology at most.
As those high school lessons taught us, men pass down Y-chromosomes, which is essentially where our masculine genes come from. Men pass down no equivalent to mitochondrial genomes.
Uniparental inheritance
We therefore each have two different kinds of inheritance. One is nuclear genomes (nDNA) that combine parts of both parents. The other is mitochondrial genomes, which exclude one parent completely.
The reason for this is far from simple. Biologists have been debating this for decades, since our intuitions tell us that combinations, which create more competition, would lead to stronger genetics.
However, for whatever reason, it seems that the opposite is true. In one experiment, mice were genetically constructed(!) to carry mitochondrial lineages from both parents. They ended up less active, more stressed, cognitively impaired, and generally unhealthy.
What is the lesson in all this? It’s hard to say. You can shoehorn in all kinds of philosophical or even political narratives, but the truth is that genetics deals with bare facts only.
In other words, what we know about our genetic makeup is grounded firmly in data. You can take it in any way you’d like, but ultimately a lot of what we take out of it is conjecture.
That doesn’t mean genetic testing is not interesting. In many ways, the most trustworthy means of knowing yourself is in your genetic makeup. Everything else – the stuff you work through in therapy! – is much more difficult to pin down. Narratives tell a constructed story, whereas genetics are a biologically accurate blueprint.
DNA testing can tell you a lot about your heritage, both ethnically and in terms of your parental lineage. How you use it, or what you choose to learn from it, depends very much on what you’re looking for.