Thursday, March 31, 2011

The Sequencing of DNA, Old School

I really like DNA sequencing. There's something about it that just interest me. Maybe it's that you can "read" people, or the thought that you're seeing something that different people don't ever get to see. And it's all possible today because Frederick Sanger saw what other people hadn't seen before. We did a worksheet earlier this week and you can see the data I collected from it above.
The worksheet had us reading DNA and protein sequences from 3 different patients and comparing them to a normal sequence of DNA/protein. A normal sequence would be seen as:


At least according to the worksheet, ;). The proteins were shown as this:

                   "Met Val His Leu Thr Pro Glu Glu Lys Ser Ala"

Don't worry, it starts getting interesting from here. As you can tell from the graph above, none of the patients have a DNA sequence that perfectly matches the norm. Abby and Bob have the most "normal" of the sequences, and it may lead you to believe that they are completely ok, just a little different. But when you look at Carol, you think,"Oh wowza, she's a mutant!"

But in reality, all of these patients have a problem. With Abby, she is only has one base change, right at the first GAG/Glu. Her's is instead GTG/Val. This is called a "point mutation". It doesn't seem like a single mutation could mess anything up, but it does. It all comes down the protein sequence. The Glu is positively charged and goes along with the sequence well, but the Val is hydrophobic. That means it will probably mutate the sequence. This is seen in people with cystic fibrosis. But she could not have! :D

With Bob, he has a Truncation mutation. He only has one changed base, like Abby. But his AAG/Lys base is a TAG/stop instead. That means that his sequence stops early, 3 early in his case. This makes the protein too short.

Carol probably has skin cancer. Her type of mutation is called a Frameshift Mutation. She has a normal sequence but is missing, it's completely gone, her T from the ACT/Thr base, so instead it is a ACC/Thr. This can be caused by radiation from the sun, or other things that could kill off one of her letters.

It makes me pretty happy that I can read all that in a single sequence. It's amazing all that can happen in a human body.
Ok, now you can take a step back, stretch, and wipe that yawn off your face. You learned something!