Friday Sprog Blogging: FSB goes CSI.

i-9be11d40a3274e05f2f54ee65d044c5c-i-ar-inosent-test-teh-dna.jpg It has been noted before that the Free-Ride offspring have a fondness for LOLcats. (After all, what six- to eight-year-old wouldn't like LOLcats?)

But it turns out that even captioned kitties can be the impetus for a conversation about matters scientific.

Oh noes!

Younger offspring: That kitty doesn't want to be caged.

Elder offspring: Because he's innocent. He didn't do the crime. Check the DNA!

Younger offspring: What do you mean, check the DNA?

Dr. Free-Ride: Do you remember what DNA is?

Younger offspring: Is that what we climbed on at the Lawrence Hall of Science?

Elder offspring: That was a model of DNA.

Dr. Free-Ride: Not actual size. But does either of you remember what DNA does?

Elder offspring: It's where the genes are.

Dr. Free-Ride: That's right. And what do the genes do?

Elder offspring: They tell your body how to make different parts?

Younger offspring: Like eyes and hair and skin?

Dr. Free-Ride: That's not a bad way to think of it. The genes carry all sorts of information about how the cells in your body should operate and make stuff. Genes help the body make proteins, and the different proteins do all sorts of important stuff to help the body grow and function properly.

Younger offspring: Did the DNA we were climbing on have something to do with spit?

Elder offspring: Yeah, wasn't it a gene for the stuff in spit that breaks down starch to sugar?

Dr. Free-Ride: You're right! It was a stretch of DNA that makes alpha-amylase, an enzyme in your saliva.

Younger offspring: So what does the cat mean, test the DNA? How will that prove he's innocent?

Dr. Free-Ride: Well, the DNA from a particular cat -- or a particular human -- is pretty specific to them. Even though that one cat's DNA would have a lot in common with the DNA of other cats, the specific genes in that DNA would probably just fit that particular cat. So if another cat did the crime -- and left behind fur or cat-spit -- the DNA in that fur or cat-spit probably wouldn't be a perfect match with the DNA from that poor, innocent kitty.

Younger offspring: You mean someone could figure out whether spit was my spit or someone else's? Even if they didn't see who spit it?

Dr. Free-Ride: If your DNA is in your spit they could.

Elder offspring: And hair and skin cells and blood.

Dr. Free-Ride: Yep.

Elder offspring: What about snot? If you sneeze, can they find your DNA in the snot, or is it just the virus that your body is trying to get rid of by sneezing it out in the snot?

Dr. Free-Ride: I suspect your DNA is in the snot, although I don't know how hard it would be to extract it from all the other snot-components.

Younger offspring: (Whispering) What about poop?

Dr. Free-Ride: That might give more information about what someone had eaten. You know that plants and animals have DNA too, right?

Elder offspring: People shouldn't poop at the scene of the crime, anyway.

Younger offspring: But a cat might.

Elder offspring: That's true. The poop might tell you that the criminal was a cat, and even what the cat had eaten, but not which cat committed the crime.

Dr. Free-Ride: My children, the cat criminologists.


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"Elder offspring: People shouldn't poop at the scene of the crime, anyway."

Words to live by.

Boy, that was funny.

"Elder offspring: People shouldn't poop at the scene of the crime, anyway.

Younger offspring: But a cat might."

The Free-Ride Progeny owe me a new monitor!!!


Oh, I wish you had been my daughter's teacher! Better yet, I wish I had had the wits and knowledge to carry on these kinds of conversations with her when she was younger. Have you ever thought about creating a book out of these conversations? It would help children grasp the kinds of questions they can ask about their world and how to go about answering those questions, AND it would model for parents and teachers the kinds of conversations that they could have with their children and students.

We use poop to genotype our mice. The Zymo Research company has the best kit we have found. It saves us from tail cutting and orbital eye bleeds - two genotyping procedures I was never fully comfortable with. For those interested, follow this link to the product's web site.

By the way, a recently caught mouse poops every 20-30 seconds. I am not sure how long they can keep that rate up, though. And in the more information than you wanted category, the larger fecal pellets are better for getting the DNA - presumably because they dislodge more epithelium on the way out.

Have you ever thought about creating a book out of these conversations?

Something is in the works. ;-)

I don't know how hard it would be to extract it from all the other snot-components.

It's pretty difficult. I used to isolate DNA from lung sputum samples, and the carbohydrate levels in mucus make the preps fairly ugly.

"But a cat might."

Hilarious! So true. The brain chillun that spring from the brains of children! This was by far my favorite spit, mucus and poopy post of the day.


Oh, man, I remember some of the conversations I had with my oldest niece when I was babysitting her and a load of AP Bio homework. Fond memories.

i think that is halariose!!!!

Teh cat burglar poops in yur shooz!

By Tsu Dho Nimh (not verified) on 14 Aug 2009 #permalink