Dr. Free-Ride: Do you guys have a view on which came first, the chicken or the egg?
Elder offspring: Do you mean the chicken or the chicken egg? Or just the egg the first chicken came out of?
Younger offspring: The first chicken came out of an egg, but it was an egg laid by some other kind of creature.
Dr. Free-Ride: And so, knowing as much as you do, you find no paradox here.
Elder offspring: But the Liar’s Paradox is still a real paradox.
Younger offspring: How did another kind of creature lay eggs that had chickens in them?
Elder offspring: Maybe mutations.
Younger offspring: What does that mean?
Elder offspring: Well, if [Dr. Free-Ride] had another baby that was really tall and had three legs and was green, that would probably be a mutant.
Dr. Free-Ride: One would hope.
Dr. Free-Ride’s better half: OK, so you know what a mutant might be like, but do you know what a mutation is?
Elder offspring: Ummm … I think it has to do with a change in a gene?
Younger offspring: What do genes do?
Dr. Free-Ride: Oh! Oh! Oh! I know this one! Call on me!
Dr. Free-Ride’s better half: (with a pronounced eye-roll) Yes?
Dr. Free-Ride: Genes code for proteins!
Elder offspring: The DNA is where the genes are, and the RNA makes the proteins.
Dr. Free-Ride’s better half: Do you remember the analogy we talked about for the DNA?
Elder offspring: Oh yeah! The DNA is like a cookbook, and each gene is like a recipe.
Younger offspring: So the RNA uses the recipe to know how to cook something?
Dr. Free-Ride: Yeah, but what they’re “cooking” is proteins that make the cells in your body do different things — telling them to be heart cells or muscle cells or skin cells —
Elder offspring: Or scales, or feathers.
Younger offspring: So how does a mutation make it different?
Dr. Free-Ride’s better half: (grabbing a cookbook off the shelf and opening it to a food-stained page) Here’s a recipe, and you can still read all the ingredients and directions pretty clearly. But what if these stains were darker?
Younger offspring: They might cover up some of the words so you couldn’t read what they say.
Dr. Free-Ride’s better half: Uh huh. And how would that affect what you’d make with the recipe?
Elder offspring: It could turn out different.
Younger offspring: Like a mutant.
Dr. Free-Ride’s better half: This recipe calls for two cups of chopped onions, but if the stains covered parts of that line you might think –
Dr. Free-Ride: Two cups of chocolate.
Younger offspring: Yum!
Dr. Free-Ride’s better half: Do you think that would make the recipe better? Or worse?
Elder offspring: Maybe.
Dr. Free-Ride: Given that this is an eggplant recipe, I’m betting on that being a deleterious mutation.
Younger offspring: We’d have to try it to find out.
Dr. Free-Ride: OK, in the interests of science, I’ll see about putting all our recipes in an electronic database that introduces random mutations in the recipes. Then you kids can give me an informed view on whether most recipe mutations are beneficial or harmful.
Elder offspring: So mutations in the DNA are like that, too? They change the recipes that get used to make the organisms.
Dr. Free-Ride: And sometimes it’s a change that ends up being good for the critters in that environment, but sometimes it’s a change that doesn’t work out at all.
Elder offspring: You wouldn’t use that recipe again.
Younger offspring: Did you know that there’s two ways we share genes with mice?
Dr. Free-Ride: Tell me more?
Younger offspring: Well, human DNA and mouse DNA are more than 80% the same.
Elder offspring: Yeah, I think I read that somewhere.
Younger offspring: And, mice can crawl into your jeans pockets and legs!
Dr. Free-Ride: That’s funny!
Younger offspring: Will you use it in the Sprog Blog?