Carl Zimmer

And in some cases, they're only looking at certain mutations in these genes like the BRCA gene.

And if you don't happen to have those mutations, they'll say, okay, you don't have a risk of breast cancer from these mutations.

But we know that people have other mutations on these genes, and they could have risks as well.

So you can't take these things at some sort of like, you know, you can't take a test result that says you don't have these mutations as meaning you will never get cancer.

It's more complicated than that.

No, there's no connection between that and the genes that influence development of your liver or your brain or so on.

It's not like just because you look like one of your parents, you are more like them in some sort of deep way.

You inherit 50% of your genes from one parent, 50% from the other.

So genetically speaking, you're just a perfect 50-50 split between your parents.

It's possible that a couple generations back, you know, your father inherited some genes that raise your risk of baldness, but then also inherited other genes that lowered the risk and maybe sort of dominated over the other genes.

And then it was just sort of a, you know, which copies of those genes that he then passed down to you and your siblings, just roll the dice.

And so for these complicated traits, you know, you may have genes that are sort of tugging that in different directions.

You know, I've had my genome sequenced and I can see that I have certain genes that raise my risk of cancer, certain genes that lower my risk of the same cancers, you know, and do they even out?

Well...

That's kind of a hard thing to know right now because we still don't know that much about these genes.

So to end up with this pattern in your family, most of your siblings, you know, being bald and you're not, like, that's what you expect from heredity.

That does seem to be quite heritable.

The sort of genetic basis of that is really still quite mysterious.

And it's an odd thing because it's only, I guess, around 15% or so of people are left-handed.

I'm left-handed.