Detective training is almost finished! Next class, our team will start investigating the mysterious theft of Buttercup's blood.
But before delving into the mystery we needed to learn one last technique: DNA extraction. The police found a tiny drop of blood on the freezer where the mammoth blood was stored--it looks like the thief got a cut while lifting the lid. Silly thief! But how does DNA help us?
Blood, as any other living tissue, has DNA, the instruction manual for life. DNA is almost identical between members of the same species. But there are differences that make each of us unique. In the case of humans, the difference in genetic information between any two people is 0.5 %. If we recover DNA from the crime scene, we can analyze it, compare it to the DNA of the suspects, and see if there's a match. Which would mean that the suspect was at the crime scene!
Going back to DNA extraction, what does that mean? It just means that you break up the cells and nucleus of the cells and set the DNA free. Then you "precipitate" it or make it come out of the solution. (By the way, in this state you can see it with your naked eye!)
DNA extraction involves a series of simple steps. We chose to extract DNA from raspberries, because it is whitish and it contrasts well with the bright red pulp of the fruit.
There! That's DNA
Did you know that you can extract your own DNA very easily? Learn how to do it in this 60' video!
The process involves some waiting so between steps we discussed the structure of the famous DNA molecule in detail, its unique shape and mode of duplicating itself. And then we built a model!
In our DNA model, the black skinny tubes represent the backbone of the DNA "ladder" and the tubes in the four other colors represent the four letters of the DNA alphabet: green for A, yellow for T, blue for G, and red for C. And remember: All Tigers Can Growl a mnemonic that tells you that A only pairs with T and C only pairs with G).
Each team of two kids built a short sequence of DNA and then we assembled it into one larger molecule.
Here's a short sequence of DNA. ATTGAAC (if we read the left strand).
Some of the bases are not joined.
Once you have the DNA, you need to obtain a "DNA profile," a series of bands that are unique to each individual, like a regular fingerprint. You do this using the technique of DNA fingerprinting. It is not difficult but it can't be done unless you have proper molecular biology equipment, which we don't have, for now, But luckily, somebody created an animation that allows you to do it virtually, and solve a funny crime. Give it a try here and figure out who stole the lollipop!
We are hoping that next class we'll have the results from the lab, which includes DNA fingerprints from the crime scene and the DNA profiles from the four suspects. Exciting!
And while we were working, snow continued piling up. And when there's snow....snowballs fly!