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)

fingerprinting

Fingerprinting; this is severely overdue but oh well.

Superglue Fuming Method

From top to bottom: Michelle, Cheryl, Yuexin, Mine.

Iodine Fuming Method

Set-up.

Mine, I think.

Power Dusting Method

Michelle's/YX's

Scraping the graphite from the pencil

Fingerprint Database

Bit blur but we all look happy :)

The pattern on my right thumb => Whorl

White Glue...Peeling Method?!

All photographs courtesy of Cheryl

Not that surprisingly, the fingerprints on my right thumb are not mirror image of my left thumb. :) (i.e. no symmetrical relationship).

SUPERGLUE FUMING METHOD

If the contrast of the white print against the black background is still too faint for a good detailed photograph to be captured, what could be done to enhance the fingerprint?

I think the dusting method, whereby coloured powder is applied and dusted off, may work since the coloured dust would attach itself to the white print so the print is more visible.

IODINE FUMING METHOD

What are the possible substances that may be used to render the prints more permanent?
Why does the print disappear?

1. iodine enhancer/fixative

2. The print is formed as a physical reaction between the iodine gas and the fats and oils on the latent fingerprint. (the fats absorb the iodine gas) We can tell it's a physical reaction from the fact the print merely changes colour; it's chemical composition doesn't change. Physical reactions are reversible; the iodine gas will sublime again. Hence the print disappears.

POWDER DUSTING METHOD

What is magnetic powder dusting and how does it work?

It's like how you would attract paper clips out of water in a tall plastic container without getting anything wet. You have a magnet on one side of the plastic sheet and magnetic iron filings or anything else magnetic on the the other side. so you drag the magnet back and forth the plastic sheet such that the magnetic stuff will stick to the fingerprint.

FINGERPRINT CLASSIFICATION

(taken from rambio2011.wikispaces.com)

Different classes have different numbers of students. Hence you cannot compare how rare or common a certain type of fingerprint is based on something like "there are more pupils in 201 with loop then the pupils in 213 who have loop. hence loops are more common in 201 than 213". It may simply be because 201 has more people in the class; so even if they have fewer percentage of people with loop, the number is still larger. That's the difference between the two graphs reflecting percentage and number.

According to the fingerprint database in the US:

• 60-65% are classified as loops
• 30 – 35% are classified as whorls
• 5% are classified as arches

Based on the 5 classes' data (and assuming that they can represent Singapore), the ranking in terms of most common and least common are the same but I think there is a higher percentage of arches in Singapore than in US, and a fittingly lower percentage of loops and whorls in Singapore.

Awareness Test

It was quite interesting how most people only take in one piece of information and block out all the other visual input when we are forced to find out one piece of information. Yet if we weren't asked to look or observe anything in particular it would be highly possible that we wouldn't observe both the moonwalking bear and the 13 passes. I was rather amused but I think the fact that people don't observe anything outside what they want to see, if that assumption can be made, is a rather sad fact in the sense that we would often miss out on so much when we are focusing on something else. I suppose when solving a crime, or any other mystery, or problem, we should be OPEN. We should not be looking for what you presume to be the only kinds of things that will give you answers; in doing so we miss out on other things which may have led us to the answer.

Mystery of the Trash Tosser

I think the raccoon is guilty.

Conditions and/or assumptions:

the only 2 suspects are a cow and a raccoon.

the trash was generated by the animal who threw the trash.

P1: Cows are herbivores.

P2: Raccoons are omnivores.

P3: There are bones in the trash dumped on the rabbit's lawn.

P4: Only animals have bones.

P5: The person who threw the trash ate bones.

C1: The person who threw the trash was the raccoon.