Roxanne Khamsi

Welcome to Science Writer.

Welcome back.

Thank you so much, Ira.

It's great to be back.

So I was taught the same thing.

I was taught that the DNA I inherited from my mother and my father is the same in all of my cells.

And what I discovered about eight years ago was that's not the whole picture and that scientists right now are uncovering that each human body is a landscape of genetic diversity and that our DNA is dynamic.

It's not static.

In fact, scientists estimate that if a person reaches 100 years old, a single white blood cell will have around 3,000 mutations that are not found in the rest of their body.

So this is the new understanding of genetics I really feel is important, that our DNA changes over time.

So part of this has to do with the fact that we are a collection of cells.

We all start as a single cell for the first 24 hours after we're conceived.

And then by the time we reach adulthood, we're around 30 to 40 trillion cells.

And that's not counting the 30 trillion cells in our gut microbiome that are microbial cells.

And there's a lot of turnover to maintain this mass of cells that we are.

Every time a cell divides, it's trying to copy its DNA and sometimes it makes errors.

And when it does make errors, those mutations, those DNA mistakes stick around in all the subsequent cells.

And on top of that, there's just like regular wear and tear that happens inside the cells of our bodies.

So DNA breaks.

And when that gets fixed, sometimes errors are introduced there as well.