The Bat that Eats Fish

**SPEAKER_1** (0:08)
You're listening to Strange by Nature, your guide to the strange, weird, unbelievable and improbable wonders of the natural world.

**Kirk Mona** (0:23)
Hello, everyone, and thanks for being here today. I'm Kirk Mona, and joining me are Rachel Gimza and Victoria Thompson. We're all naturalists who together have scoured the world for weird and wonderful wonders, just to please your mammalian brain's desire for novelty. Isn't that nice? Let's do this.

**Victoria Thompson** (0:44)
Well, hello, everybody. Welcome back to the show.

**Rachel Gimza** (0:46)
Hey.

**Victoria Thompson** (0:47)
Good to be with you guys as always.

**Rachel Gimza** (0:49)
So excited.

**Victoria Thompson** (0:50)
I am starting us off this week, and you two know how much I love to talk about horrifying medical conditions.

**Rachel Gimza** (0:57)
Oh, God.

**Kirk Mona** (0:59)
Oh, dear. What a joy. Uh-huh.

**Victoria Thompson** (1:03)
Yes. I'm going to do that today.

**Kirk Mona** (1:05)
Is that what we're doing?

**Victoria Thompson** (1:08)
I'm actually going to talk about a whole category of medical conditions that can actually range from the relatively minor chronic up to the level of, you know, please let me move somewhere where euthanasia is legal. So.

**Kirk Mona** (1:21)
Oh, my God. Oh.

**Victoria Thompson** (1:26)
Uh, a lot of. So I'm going to talk about genetic diseases.
And a lot of well-known genetic diseases are recessive. This kind of makes sense. So quick review for our listeners who may have forgotten some of their high school biology. You have 46 chromosomes that carry all of your DNA, and half of them are from your mom and half of them are from your dad. They all have the same genes on them, but the ones from mom and dad can have different variants of the genes. Uh, and some genes are recessive and some are dominant. So what that means is the typical example that's used in, like, high school biology is eye color.
Uh, there's a little more nuance to this in the real world, like, with everything, but we're just gonna go with the simple story.

**Rachel Gimza** (2:16)
Yeah, like, my niece has gray eyes, and her dad has really dark brown eyes, and her mom has really, really bright blue eyes.

**Victoria Thompson** (2:25)
Yeah. Well, so what we're gonna go with is brown is dominant and blue is recessive. So a person can have one brown eye gene from one parent and one blue eye gene from the other parent, but their eyes will be brown because the brown kind of overpowers the blue. In order to have blue eyes, you need two copies of the blue-eyed gene.
This is the way a lot of well-known genetic disorders work. For example, sickle cell disease, cystic fibrosis, Tay-Sachs disease. These are all what are called autosomal recessive. So you need both copies of the gene in order to get the disease. Right. These are horrible, deadly diseases that often start showing up in infancy or childhood. And especially before modern medicine, it usually led to quite early deaths for the unfortunate people who have them.
But these diseases persist because it's possible to have only one copy of the diseased gene and still be healthy. So it gets passed on from generation to generation.

**Kirk Mona** (3:23)
Like me. Yes.

**Rachel Gimza** (3:25)
Yep. Yep.

**Victoria Thompson** (3:32)
In fact, for some diseases, there's actually an advantage to having one copy of the gene. The most well-known of this is the sickle cell gene, which confers resistance to malaria. So if you have one copy of the gene, you're resistant to malaria. If you have two copies, you're in for a really bad time.

**Rachel Gimza** (3:47)
Yeah.

**Victoria Thompson** (3:50)
But what about autosomal dominant diseases? That's actually what I want to talk about today.

**Rachel Gimza** (3:55)
Huh.

**SPEAKER_1** (3:56)
I guess I don't think about that.

**Victoria Thompson** (3:58)
Yeah, most people don't.
They're sort of less well-known for the most part. So these are diseases where you get one copy of the gene, you have the disease.

**Kirk Mona** (4:10)
Oh, that sounds terrible.

**Rachel Gimza** (4:12)
That sounds real bad.

**Victoria Thompson** (4:14)
So if you think this through, you'd figure that these diseases would be milder or chronic types of diseases, and something that kills you off quickly is not going to have a chance to be passed down to the next generation, right? Yeah. And to some extent, this is true.
Some of the most common autosomal dominant disorders, I don't know if you can even call all of these diseases exactly. One is achondroplasia, which is the most common form of dwarfism.

**Kirk Mona** (4:44)
Okay.

**Victoria Thompson** (4:45)
Neurofibromatosis type 1, which causes benign tumors to grow on the nerves all over the body, which these are conditions that can certainly cause complications and can be debilitating, but it's perfectly possible to have a relatively normal life, get married, have children while still having these diseases.