Monday 5 September 2011

DNA testing

1. hydrogen peroxide

 Top right: sample 1, Top middle: sample 2, Top left: sample 3, bottom right: sample 4, Bottom middle: sample 5, Bottom left: sample 6
After adding hydrogen peroxide, samples 4, 5 and 6 bubbled.

Results: 
Sample 1
My prediction: May be blood -> Red 
Observation: No bubbles
Result: Negative 

Sample 2
My prediction: May not be blood -> Orange
Observation: No bubbles
Result: Negative

Sample 3
My prediction: May not be blood -> Pink 
Observation: No bubbles
Result: Negative

Sample 4
My prediction: May be blood -> Red and quite thick
Observation: Bubbles!
Result: Positive

Sample 5
My prediction: May not be blood -> Purple 
Observation: Bubbles!
Result: Positive

Sample 6
My prediction: May not be blood -> bright red with small particles flatting around 
Observation: Bubbles!
Result: Positive

Conclusion: Samples 4, 5 and 6 may contain blood as hydrogen peroxide reacts with blood and bubbles. 

2. Luminol testing
 Spray Luminol on all three samples
 Notice sample 4(one on the left), it glows
Notice that sample 5 also changes colour
 Notice that the colour of all three samples are different

Results: 
Sample 4: Glowed when luminol was applied
Sample 5: Glowed when luminol was applied
Sample 6: Didn't glow

Conclusion: Sample 4 and 5 may be blood as Luminol chemiluminescence can react with a number of substances such as copper or copper-containing alloys, ; and, as a result, producing the typical blue glow

3. Kastle Meyer Reagent 
 Before adding the reagent 
 After adding reagent

Results: 
Sample 4: Changed colour -> pink
Sample 5: No change
Conclusion: Sample 4is blood


DNA extraction
We also extracted DNA from our cheek cells but unfortunately, i didn't take any pictures. 


DNA notes

DNA
What is DNA? 


DNA, or deoxyribonucleic acid, is the hereditary material in humans and almost all other organisms. Nearly every cell in a person’s body has the same DNA. Most DNA is located in the cell nucleus (where it is called nuclear DNA), but a small amount of DNA can also be found in the mitochondria (where it is called mitochondrial DNA or mtDNA).
The information in DNA is stored as a code made up of four chemical bases: adenine (A), guanine (G), cytosine (C), and thymine (T). Human DNA consists of about 3 billion bases, and more than 99 percent of those bases are the same in all people. The order, or sequence, of these bases determines the information available for building and maintaining an organism, similar to the way in which letters of the alphabet appear in a certain order to form words and sentences.
An important property of DNA is that it can replicate, or make copies of itself. Each strand of DNA in the double helix can serve as a pattern for duplicating the sequence of bases. This is critical when cells divide because each new cell needs to have an exact copy of the DNA present in the old cell.



Gene: 
-> Are made up of DNA
-> contain the instructions on building the proteins that enable our bodies to function


Chromosomes
XXY Syndrome => Kleinfelters Syndrome. This disorder affects only boys. 
Symptoms: development of breasts, spare facial hair, and an inability to produce sperm.

XYY Syndrome affects only boys. There are no noticeable physical differences with this disorder. 
Symptoms: increased activity, delayed mental maturity, and in creased tendency for learning problems in school.

XXX Syndrome =>Triple or Triplo X. This disorder affects only females. Again, there are no physical indications of Triplo X. 
Symptoms=> possible delayed menopause, and increased probability of delayed development in motor function, speech, and maturation

XO Syndrome =>Turner Syndrome and affects only girls. There are minimal physical abnormalities and Turner’s does not affect intellect. The primary effect of Turner’s is due to the missing X chromosome. This causes infertility.



Chromosomes: 44+x
Female: XX chromosomes, 
  • can be divided into two ‘X’ chromosomes 
  • double ‘X’ and ‘O’
Male: XY chromosomes
  • can be divided into ‘X’ and’Y’ chromosomes
  • double ‘Y’ and double ‘x’

Chromosomes => genes wrapped around a protein
- Egg has 23 pairs of chromosomes, sperm 23 pairs chromosomes
- Female has only X chromosomes, however a male has both X and Y chromosomes
- All homosapiens need at least 1 X chromosome. A Y chromosome by itself will be aborted.

Saturday 6 August 2011

Blood splatter

Blood splatter 1 
 Blood Splatter 2
 Blood Splatter 3
 Blood Splatter 4
Blood Splatter 5
Blood splatter Pattern from a Laboratory Experiment by Mr Leong TK & Chua HL

What is the shape of the blood splatter?
It is mostly round and oval.

Describe any other characteristic of the splatter
1. Drip
2. Slammed against the thing
3. The person staggered and collapsed 
4. Slammed repeatedly against the wall, slid down

What are the factors that affect the shape of the blood splatter? Name as many as possible.
- Size of wound
- Depth of wound
- Position of person
- Height of the person
- Contact with blood splatter 

Generate some hypothesis from the blood splatter patterns observed above. 
- The greater the angle of elevation, the longer the blood splatter
- The greater the angle of elevation, the narrower the blood splatter
- The greater the angle of elevation, the smaller the angle of impact
- The larger the distance between the the blood splatter and the wound, the wider the blood splatter

Experiment one: Height

Height/cm
WA / mm

WB / mm

WAve / mm

10
8mm
8mm
8mm
30
10mm
11mm
10.5mm
60
11mm
12mm
11.5mm
100
13mm
13mm
13mm
150
12mm
14mm
13mm


Experiment 2: Angle 

Angle of elevation / °

LP / mm

LQ / mm

LAve / mm

WP / mm

WQ / mm

WAve / mm

10
13mm
15mm
14mm
13mm
14mm
13.5mm
30
15mm
16mm
15.5mm
13mm
13mm
13mm
50
19mm
19mm
19mm
11mm
11mm
11mm
70
28mm
26mm
27mm
9mm
9mm
9mm



Graphs: 
Height (Width) 


 Angle of elevation ( Length)
 Angle of elevation(Width)
 Angle of elevation VS angle of impact

Pictures: 
 Experimental Set up
 Blood splatters ( Height)
 Blood splatters (Height)

Blood splatters (angle)

Part 2: 
This is the blood splatter patterns created by my group. 
Analysis:
 From this activity, I gathered that all my hypothesis were true. 
1. Height: This factor was a little difficult to test out as the butcher sheet was pasted vertically on the wall, but nevertheless, true. 
2. Angle of elevation: From the blood splatter patterns made, it shows that blood splatters are longer and narrower when blood is dripped from a certain angle. 
3. Angle of impact: The above pattern shows that the angle of impact is smaller when the blood is dripped from a certain angle. 

Explanations: 
Height
The height from which the droplet falls affect the velocity of the droplet of blood. The velocity of the blood will in turn affect the width of the blood splatter. So, as the droplet remains airborne for a longer period of time, the velocity of the droplet changes, causing the width of the splatter to change as well. 











Angle of Impact

The angle of impact on a flat surface can be calculated by measuring the length and width of a stain. The angle of impact is the acute angle that is formed between the direction of the blood drop and the surface it strikes. The stain will be more elliptical when the angle of impact increases. This is an important measure because it is used to determine the area of convergence and the area of origin.

- Elongation
As the blood splatter is elongated, the width of the splatter becomes narrower. The angle of impact will also increase when the difference between the length and width of the splatter increase.

Chromotography

-> Used to separate mixtures of substances into their components
-> Stationary phase: a solid, or a liquid supported on a solid
-> Mobile phase: A liquid or a gas
     => Flows through the stationary phase and carried the components of the mixture with in. Different components travel at different rates.

Retention Factor - Rf
- Unknown substances separated by chromatography can be identify by Rf values
- Rf value = Distance move by substance/distance move by the solvent

Uses
- Separate and identify compounds in a mixture
- For colourless compounds, at the end of the experiment, the chromatogram is sprayed with a locating agent
- The locating agent is a chemical substance that will produce colored products on reaction with colorless compounds

Paper Chromatography
- Stationary phase: Uniform absorbent paper
- Mobile phase: Suitable liquid solvent or mixtures of solvent
- Separate a mixture of solutes with different solubility and degree of absoption

Wednesday 3 August 2011

Flame test

Origin of Flame Colours

  • Flame colours are produced from the movement of the electrons in the metal ions present in the compounds.
  • For example, a sodium ion in an unexcited state has the structure 2.8.1.
  • When you heat it, the electrons gain energy and can jump into any of the empty orbitals at higher levels, depending on how much energy a particular electron happens to absorb from the flame.
  • Because the electrons are now at a higher and more energetically unstable level, they tend to fall back down to where they were before - but not necessarily all in one go.
  • An electron which had been excited from the 2nd level to an orbital in the 7th level, for example, might jump back to the 2nd level in one go. That would release a certain amount of energy which would be seen as light of a particular colour.
  • However, it might jump back in two (or more) stages. For example, first to the 5th level and then back to the 2nd level.
  • Each of these jumps involves a specific amount of energy being released as light energy, and each corresponds to a particular colour.
  • As a result of all these jumps, a spectrum of coloured lines will be produced. The colour you see will be a combination of all these individual colours.
  • The exact sizes of the possible jumps in energy terms vary from one metal ion to another. That means that each different ion will have a different pattern of spectral lines, and so a different flame colour.


By adding different metals into a flame, the colour of the flame would change.
The colours of the flame
Barium - pale green
Calcium - red-orange
Copper - blue-green
Lead - White-blue
Potassium - Lilac
Sodium - Bright yellow

 Copper 
 Sodium 
Potassium 

Here's a cool video!!


However, there are some substances that does not change colour when added to the flame. This would mean that the substance added is not a metal.


Human remains

The human body contains only about 1g of silicon and this is the element that will survive the heat of the crematorium oven. The content in the urn will therefore be less than 1%, a small fraction of the human ashes.
The analysis in the lab showed that the percentage of silcon is 19% hence proving that it can't be of human origin.



The videos showing the different flame colours will be uploaded soon

Fingerprints homework

Fingerprinting is commonly viewed as an infallible means of personal identification as forensic science has proven that the two human beings are not likely to have the same fingerprints. It has also been suggested that the fingerprints of any individual do not change throughout his/her lifetime with the exception of a significant injury that results in scaring on the finger(s).
There are three main types of fingerprints: visible prints, latent prints and impressed prints. Visible prints are also called patent prints and are usually left in some medium that reveals them to the naked eye. They can be formed when substances such as blood, dirt, ink or oils on the finger come into contact with a smooth surface a leave an impression that is visible without development.
Impressed prints are also called plastic prints and are indentations left in soft pliable surfaces, such as clay, wax, paint or other surface that will hold the impression. They are visible and can be viewed or photographed without development.
Latent prints usually refer to prints that are not apparent to the naked eye. They are formed from the sweat from sebaeceous glands on the body or water, salt, amino acids and oils contained in sweat. The various fluids create prints that must be developed before they can be seen or photographed. They can be made sufficiently visible by disting, fuming or chemical reagents.

Ridges and Pores activity
Introduction:
A friction or epidermal ridge is a raised portion of the skin on the fingers and toes. Impressions of fingerprints may be left behind on a surface by natural secretions of sweat from glands that are presnet in friction ridge skin.

WOOD GLUE method
AIM: To capture ridge and pore details of your finger using a polymer cast.


- Where are the pores found? Are they regularly spaced?
The pores are usually found against the fingerprint ridges. They are regularly spaced.
- Are the lines of your print equally spaced throughout?
Yes, they are. However, even though they look quite evenly spaced, but the spaces may be very equal. 

Cyanoacrylate (Superglue) fuming method
Introduction:
The actual development of this chemical method of developing latent fingerprints is somewhat unclear as many agencies and countries claim credit for its discovery. What is generally accepted is that the method came about between 1977 and 1978. It has since been used as an effective technique in many crime laboratories throughout the world.
The basic concept behind all chemical techniques is to apply something that will chemically react with one or more of the constituent chemicals of latent fingerprints. The product of the chemical reaction will render the fingerprints visible and allow the print to be photographed so that identifications can be made.
Superglues typically contain methylcyanoacrylate or ethylcyanoacrylate. They react with traces of amino acids, fatty acids and proteins in the latent fingerprint and the moisture in the air to produce a visible, sticky white substance along the ridges of the fingerprint. The resulting image is then photographed so that comparisons can be made with other fingerprints that are collected.
To enable such a reaction to take place, the cyanoacrylate must be in its gaseous form. Hence, investigators tend to use a fume box to hold the chemicals and objects in an enclosed space. Heat is then applied to allow the superglue to vapourise. If there are any latent fingerprints on the object, the exposure and humidity in the atmosphere will be sufficient to enable the reaction to take place. The actual amount of time required for such a reaction to take place depends on several factors: concentration of cyanoacrylate fumes, humidity levels and size of fume box etc. It is often required to monitor the reaction as it is almost impossible to predict the actual amount of time required for the prints to develop.

AIM: To develop latent prints on a non-porus surface using 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 caputured, what could be done to enhance the fingerprint?
Flourscent dye can be applied onto the print and then placed under UV light to make the print visible. 

iodine fuming method
Introduction:
The iodine fuming method has historically been recognized as one of the earliest techniques used by investigators for developing latent prints. Prior to the introduction of chemical methods such as using ninhydrin and silver nitrate, iodine fuming was a preferred and recommended method to be used on paper products. 
While frequently categorised as ‘chemical technique’, the development of latent prints with iodine fumes is not a chemical process but a physical one. Chemical reactions produce new substances and will result in changes of the properties of the constituents of the latent print. Eg. Silver nitrate reacts with the chloride from sodium chloride to form a white precipitate – this creates white lines that make up the latent print. 
However, in iodine fuming, natural body fats and oils in the larent print temporarily absorb the iodine vapours. This results in a change in colour, often from colourless to dark brown. This temporary change fades with time as the iodine that is absorb will eventually dissipate into the atmosphere. The colour change can be made permanent by the application of certain materials but the developed latent print can usually be photographed at the greatest inensity of colour change and then allowed to fade. 
One advantage of using iodine fuming is that it is an essentially non-destructive technique. No permanent or chemical change has taken place after the print develops. The latent can therefore be further processed using other methods. Additional tests for the constituents of the latent can also be conducted after the print is developed.
AIM: To develop latent prints on a porus surface using iodine fuming method.


- What are the possible substances that may be used to render the prints more permanent? 
A water and starch solution. 
- Why does the prints disappear?

Powder dusting method
Introduction:
The most commonly known method for developing latent prints would probably be the powder dusting method. A variety of powders are used in dusting for prints. Many of these powders contain aluminium or carbon. The finely crushed powder is gently applied to a surface and the minutes particles of powder cling to the latent residue, making it visible. These prints are then lifted using adhesive tape. For dusting to work, the surface that is being dusted must be completely dry and relatively free of other contamination.
The principle behind dusting is simple. Oils and perspiration form the common residue on fingers that get transferred when a print is made. When the powder is applied to the surface with the print, it sticks to the oils and brings out the ridge patterns. 
Dusting is ideal on wood, metal, glass, plastics and tiles. It is less than ideal on paper, cardboard and leather. Powders vary in colour, stickiness, photographic and magnetic qualities. The best colour to to use is one in shart contrast to the surface colour. For example, a white or grey powder works best on a dark surface and a black powder works best on a white or colourless surface. In multicolour situations (such as a magazine cover) it is best to use a fluorescent powder. When the dusted object is exposed to ultraviolet light, the powder will glow, making the print show up regardless of the background colour.
Aim: To develop latent prints using powder dusting method


- What is magnetic powder dusting and how does it work?
Magnetic powder dusting is the used of magnetic powder to reveal fingerprints. Magnetic powder dusting does not require a brush, unlike regular dusting. By using a magnetic wand, the powder would be attracted to the wand and as the wand moves, thus, only the powder alone would move over the print. 


Classification and identification of fingerprints
Introduction:
It is not clear which civilisation first utilised fingerprints as a form of identification. Evidence suggests that ancient Egyptians and Chinese create fingerprints on clay objects and official documents as a form of identification. There are however no known documents that describe how identification was conducted in ancient times.
Modern development of fingerprinting was mostly documented from 1858, when Sir William Herschel, British Adminstrator in District in India, required fingerprint and signatures on civil contracts. In 1892, Sir Francis Galton, a British Anthropologist and cousin to Charles Darwin, published the first book on fingerprints. He identified the individuality and uniqueness of fingerprints. In 1901, the first fingerprint bureau was eastablished in Scotland Yard. The system of classification was developed by Sir Edward Henry and is still the basis on which modern automated systems work to compare and identify fingerprints. 
The three basic fingerprint patterns are Whorl, Arch and Loop. There are more complex classification systems that further break down the pattern to plain arches or tented arches. Loops may be radial or ulnar. Whorls also have more detailed classifications.
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




Number: 
Finger Pattern
210
213
arches
1
5
whorls
14
8
loops
18
15
Graph












Percentage: 
Finger Pattern
210
213
arches
3.03
17.86
whorls
42.42
28.57
loops
54.55
53.57

100
100