Summary of how DNA works

About a week ago (I think), I got my DNA! So what exactly is our DNA?

Using this website, I found out the following:

DNA - Something in our nucleus that gives cells in our body instructions necessary for a living organism to grow and live. Deoxyribonucleic acid is a double helix (somewhat like a twisted ladder) formed by A, C, T and G which are bonded by hydrogen.

Genes - A bigger unit of DNA

Proteins - Essential for all body processes (from what it seems)

So how does the DNA become a protein? Last time during bio revision I watched some video. So I just rewatched it.

Apparently something in the nucleus reproduces the DNA such that it becomes mRNA (this super similar thing)

This goes to the ribosome.

At the same time, amino acids are carried my transfer RNA (if I remember correct! >.<) cells to the ribosome. Tested for a code-on/anti-code match with mRNA (at A-site).

If match, then tRNA shifted to P-site, where the amino acid it carried is added to amino acid chain.

Then the used tRNA will be recycled after being ejected from E-site.

http://www.youtube.com/watch?v=TfYf_rPWUdY

Blood Spatter Analysis

What are these? Guess.

My guess: Arterial Spurt (some major artery was severed (not sure if that's the right word heh) and the heart is still pumping so the blood is sprayed on the wall)
My guess: I suppose the big circle at the right is something from a syringe I don't really know what's happening at the left side.
My guess: no idea.

My guess: I seriously have no idea.

Answer these questions!

What is shape of blood splatter?

I suppose it would include, among others, the length/direction of the tail/length of the blood splatter, diameter if it's round

Describe any other characteristic of the splatter.

The surrounding tiny spots of blood, or maybe something like the bottom is like thicker or something cause of gravity.

What are the factors that affect the shape of the blood splatter? Name as many as possible.

- Height (the higher the bigger)

- Angle at which the blood hits the surface

- Direction

- Velocity

- Something about the weapon used? I'm not sure which aspect of the weapon but there's a difference between a syringe and a knife for example.

Generate some hypotheses from the blood splatter patterns observed above.

The greater the height from which blood is dropped, the greater the diameter.

Data Analysis:

Height/cm	Diameter of A/mm	Diameter of B/mm	Average Diameter/mm
10	9	9	9
30	11	11	11
60	13	13	13
100	16	15	15.5
150	15	15	15

The greater the height from which the blood is dropped, the greater the average diameter of the blood spatter produced.

Angle tilted by board/o	Angle of impact	Width (P)/mm	Width (Q)/mm	Average Width/mm	Length (P)/mm	Length (Q)/mm	Average Length/mm	Theoretical Angle of Impact
10	80	11	13	12	11	13	12	90.0
30	60	13	13	13	14	15	14.5	63.7
50	40	12	11	11.5	17	28	22.5	30.7
70	20	8	7	7.5	35	45	40	10.8

I'm still trying to get why is sin-1 (width/length) is the angle of impact. maybe it's cause it's afte rmidnight already. will try to understood soon. Anyway the theoretical angle of impact is not the same as ours; maybe experimental error.

Quad-rio? (whatever you call a group with 4 people) Task

(special thanks to audrey for the monologue and shirley for the camera-ing.)

Chromatography

(Same lesson as flame test lesson)

group member: yixin

Our chromatography was quite failed. But oh well.

Step 1. Cut up portions of the cheque amount in $. In this case, '9', '0', '0', '0', '0'.

Step 2. Drop a few drops of ethanol into 5 microfuge tubes and label them '1' to '5'.

Step 3. Place the cut up numbers into the tubes, making sure the digits 1 to 5 correspond with the ordinal number of the digits on the cheque.

Step 4. Draw a line 5cm from the bottom of the 6 strips of chromatography paper.

Step 5. Use a capillary tube to drop one drop of the ink from each of the microfuge tubes onto the line on the chromatography paper, and label the chromatography paper accordingly.

Step 6. Dot one strip of chromatography paper with Marker 1/2 (depending on the group)

Step 7. Pour water into the boiling tubes and clip the chromatography paper to the tubes such that the water is just below the drop of ink/the pencil line (oh dear I think I forgot my chem...)

Step 8. After a period of time take note of the solvent front and calculate the retention factor (Rf value)

I think we didn't exactly plan our methodology properly (The above is sorta edited), hence the marks weren't very clear and we didn't manage to solve the mystery. :(

We experimented with the following metals:

Barium

Calcium

Copper

Lead

Potassium

Sodium

We wet metal loops and then put powdered samples of barium chloride and crystals of the other metallic compounds on the metal loops and put them over a non-luminous flame, causing changes in the flame colour.

Colour of flame with different metals

Barium: Yell0w-Orange

Calcium: Orange-Red

Copper: Green

Lead: White

Potassium: Lilac

Sodium: Yellow

How and what is it used for in "crime scene investigation/forensic science"?

By identifying trace elements, you can find out what the victim has been in contact with. E.g. in blood if you find trace elements then you can find out any potential murder "weapons" (in the form of substances).

If there's more than one trace metal present, is the flame test still suitable to identify the trace metals?

Some machines may have to be involved since under such a scenario the naked eye can only see one dominant colour. But I think even this has limitations.

Is the flame test sufficient to identify the trace metal(s) present?

I doubt it. Some metals do not change the colour of the flame at all. Also the amount of metal may not be substantial enough to produce a distinct distinguishable colour.

What is a "Mass Spectrometer"?

measures mass of electrically charged molecules (will try to understand and update)