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.

Heheh Data from our blood splatter experiments :D

For the height versus diameter of blood drop:

The graph:

For the angle of inclination versus length and width of blood splatter:

The graph:

Blood Splatter Analysis :DD

Teehees see the video for our analysis :)

Blood Splatter - guesses

This blood splatter might be formed by a blood drop hitting the surface at a near distance and at a rather fast speed. It is possibly dripped from a cut wound.



This blood splatter is very hard to explain. The splatter is circular yet with a certain area that does not have blood in a strange way. The smaller splatters also trail the big one strangely. The blood can be dripped from a cut wound and smudged in a certain way. Otherwise there can be something at the wound or on the surface that results in the clear space on the splatter.


This elongated blood splatter is formed by blood hitting the surface and  splattering in one particular direction, leaving an irregularly shaped splatter.  This can be formed by blood that is spurting out at a fast speed and hit the surface at an angle in a certain direction.



A large amount of blood impact the walls at a close distance, and subsequently drips down the wall. It can be caused by cutting a person with powerful weapons such as chain saw, and the large amount of blood spurts out.



Answer the following questions in your journal:

1. What is shape of blood splatter?
2. Describe any other characteristic of the splatter.
3. What are the factors that affect the shape of the blood splatter? Name as many as possible.
4. Generate some hypotheses from the blood splatter patterns observed above.

1. The blood splatter is circular in shape, with ragged edges. It can be elongated in one direction forming an oval, when impact is from a certain angle. 

2. The edges are ragged and uneven, There is an area inside of the edges of each splatter showing where the blood pooled. 

3, Speed of the impact, distance of the source from the surface, forcefulness of the impact, direction of the impact, angle at which blood hits the surface.

4, The greater the angle at which the blood hits the surface, the more elongated in length the splatter would be in the direction of the movement of the impact. 

More videos for flame tests!

Another video of what I think is the sodium element which burns orange first before turning yellow in the last few moments right before all the crystals are burnt.

This element giving out bright green light when ignited is of course copper :) it is so pretty.

In this video, we ignited copper and sodium together. If the video quality is better there can be seen more clearly bright green flame and orange turning to yellow flame burning alongside each other.

Demonstration by Miss Tan! Aerosol sprays are used to spray the dissolved crystals of the elements into the fire. Elements demonstrated include potassium, calcium and copper.

Here the elements are put into a bowl and fire set to it. The colours are not as obvious however, due to the fact that alcohol is needed to keep the fire burning, and alcohol itself gives out a blue flame when burnt.

Videos from flame tests!

It's a pity because as far as we found, the videos can't be shown in iPhoto album :( and we took nearly all videos. But at least I can put it up here :)

The element gives off white light when burnt.......should be magnesium.

This element gives off orange/yellow light. It is probably calcium.

Giving off red and a little magenta light, this element may be lithium.

This element gives off orange light when  first ignited, but towards the end the light emitted becomes bright yellow. It can be sodium.