DNA Fingerprinting

For the first lesson about DNA profiling we did in class, we examined the traits of ourselves and members of our group, and identify our trait number to see if we have a twin in this class. But most people seemed to have the same traits, like right-handed, straight hair, no widow's peak, etc. So a few trait numbers are really common, like mine which is 32. It was also really interesting to examine the mid-finger hairs using that microscope connected to an iPhone. I never knew such equipment existed. So convenient, yet so complicated!

We did a keynote about our findings but which was unfortunately deleted when Vivian's mac crashed :( now we're setting about to do a new one, so no keynote up yet.

For the lab session, first we did the tests for which liquid was real blood. It was very interesting; for example, I never knew that there was no definite test for blood, because in all the detective shows they show investigators determining whether a stain is blood just by using one chemical. I like the Luminol test the best; so all the CSI shows about following a glowing trail of blood is true! Janelle was fascinated by all the bubbling from the hydrogen peroxide test and was creative enough to mix different samples together and make them bubble even more. But the foam is nearly solid, really quite cool. I wonder what the other chemical - sample 5 - is, because it is so much like blood and it emits such a foul smell every time it reacts. Not to mention that for all the tests, it reacts to turn dull brown. It must be a very interesting chemical. I forgot to ask Ms Tan in class though.

Then we need the experiment to obtain our DNA. Mine didn't turn out well; on second thoughts, I think I left the 100 Plus in my mouth for too short a period of time, and I didn't swish the liquid around my mouth  enough, so there wasn't a sufficient amount of cheek cells there. Another reason is that when I put in ethanol in the end, I forgot to let it dribble down the side at first as I was too excited, and I think that destroyed some of the DNA. Still, I could see a few strands of it....but all was destroyed when I shook it, too much.

That would be all from the experiments.

Questions:
1, Why is it necessary to use more than one test to determine whether the given stain is blood?
That is because there is no one definite test for blood. Each test only corresponds to the presence of certain chemicals in the blood and distinguishing it from substances without that chemical; only by determining that the sample has a combination of the distinctive chemicals present in blood, can we conclude it is blood.

2, Once I know the sample is blood, I will send it for DNA fingerprinting.