Dalton Conley
speaker
46 appearances
1 recordings
1 series
first heard Apr 2025
last heard Apr 2025
Dalton Conley’s voice in public audio — every appearance, attributed to the second.
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Thanks for having me, Lynn. My pleasure.
Sure. When scientists started decoding the human genome, many assumed the nature-nurture debate was over and that soon we'd know the genetic blueprints for everything obesity, intelligence, susceptibility to chronic disease, even individual personality traits.
Pharmaceutical companies would develop drugs that could target the handful of genes responsible for, say, arthritis or heart disease or schizophrenia. The end of illness would soon be at hand. But it wasn't that simple.
No, there's no one gene for any of those chronic diseases that affect so many Americans. In fact, there's not even a handful of genes, much to the chagrin of the scientists who had first worked on the Human Genome Project in a few short years after the human genome was decoded in 2003. We learned a hard lesson, which is
Most things we care about, everything from height to schizophrenia to arthritis to heart disease, you name it, is highly polygenic, which means that it's not controlled by five or six genes, but it's controlled by hundreds of genes across the whole genome, thousands of locations in your chromosomes.
That was a huge disappointment because that meant that you couldn't easily just gene edit or develop a pharmaceutical to knock down or enhance a handful of genes to fix the problem.
When the human genome was decoded, there was a betting pool. How many genes are humans going to have? Lowly corn has 100,000 genes. It turned out that we had only 20,000 genes, which nobody was even close. And what that means is that those 20,000 genes are doing a lot of work
In every cell in your body, you have the exact same blueprint, but your skin cells are obviously very different than your liver cells and your brain cells. So gene expression is the switching on and off of those genes in those particular cells that make a brain cell unique or different from a skin cell. Those switches, the gene expression changes.
are also affected by the environment, which is a very exciting area of research as well. So if you have a lot of stress in your life, genes for cortisol receptors are going to be switched off, for example, because you've had too much stress for too long. So yes, it's a way that the environment comes under our skin and affects how our genes work.
Exactly. And it's usually not an on-off switch. I should say it's more like a dimmer, but in certain cells or in certain conditions, certain times of life, you'll produce more of this genius protein or less of it. And it's usually not just completely off or completely on.
Biologists have known that you can't talk about genes independently of the environment or the environment independently of genes. But what's really exciting as of late is that we now have tools because we've measured the whole human genome and we have a lot of data that we didn't have before that measures millions of people's genomes.
We can construct these polygenic scores that predict outcomes like schizophrenia, educational attainment, height, body mass index, you name it, there's a polygenic index for it. That is a tool for us to see how genes and environment interact. And genes and environment interact in three ways.
And the first is, I'll give the example that you mentioned, is imagine a kid that's born with two working copies of the sprinter's gene, the fast twitch muscle gene that almost all elite athletes have. She's going to probably be picked up. First, when they choose upsides in the schoolyard, she's probably going to win all the games of tag or races in school.
Maybe she's going to be spotted and picked to go into organized sports and she's going to excel there. All that exposure, all that environment of getting chosen to be on an organized sports team, getting more investment in terms of summer camps and training. That's environment, but it's a result of her genes.
It's a mechanism by which her genes are going to have the effect of making her, let's say, a division one athlete when she gets to college. A second aspect of how genes and environment are kind of indistinguishable is that
The environments we encounter, your parents, of course, your siblings, your peers at school, your coworkers, they all matter to how you turn out or how you behave or your health, but they're partly made up of the genes inside their bodies. And we can show that, for example, If you marry somebody with high polygenic index for depression, that affects your likelihood of becoming depressed.
In fact, the effect of your spouse's genes on depression are a third, almost as big as your own genes inside your body in terms of influencing your likelihood of depression. The genes of your classmates at school affect your likelihood of smoking almost as much as your own genes do. I call that the social genome or the environment is really genetics one degree removed to some extent.
And then the third way is that when there are massive environmental shifts, genes can matter more or less. So in the early 20th century, calories were scarcer, physical labor was more routine for most of us, and obesity was pretty rare. And genes didn't predict who was heavier or thinner.
But fast forward to today in our calorie abundant world and our more sedentary lifestyle, and the population is heavier, the distribution of weights is wider. And it turns out that genetics predict where you fall in that distribution much more than they did before. So those are the three ways genes create the environment they want or need, so to speak. The environment is in part genetics.
One degree removed is the genes of the other people around you affecting you. And third, the environmental landscape influences how much genes matter or don't matter.
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