Tuesday, August 23, 2011

CSI Lesson Eight(24/08/2011)


DNA profiles vary from person to person.
When profiles from a single VNTR locus from unrelated individuals are compared, the profiles are normally different.
However it is POSSIBLE for 2 individuals to have the same profile are 1 - 2 loci
The chance of more than 1 person having the same DNA profile at 4, 5 or 6 different VNTR loci is extremely small.
So what is DNA Profiling and how can we make it a reliable piece of physical evidence in court?
Each of us has a unique DNA profile or fingerprint. A technique called electrophoresis is used to obtain DNA profiles, relying on sections of our DNA that are known as non-coding DNA (DNA that does not code for a protein). To make it a reliable evidence, forensic scientists can obtain different sets of DNA and run electrophoresis on it, analysing the number of tandem repeats and the number of bands which are identical between the suspect and the DNA evidence.

How can DNA be used to identify an individual?
Almost every cell in our bodies contains DNA, the genetic material that programs how cells work. 99.9 percent of human DNA is the same in everyone, meaning that only 0.1 percent of our DNA is unique!
Each human cell contains three billion DNA base pairs. Our unique DNA, 0.1 percent of 3 billion, amounts to 3 million base pairs. This is more than enough to provide profiles that accurately identify a person.

What is DNA Profiling?
Living organisms that look different or have different characteristics (traits) also have different DNA sequences. The more varied the organisms, the 
more varied the DNA sequences.
DNA fingerprinting is a very 
quick way to compare the DNA 
sequences of any two living 
organisms or more,


How to make a DNA Profile

1. Isolation of DNA

2. Cutting, sizing, and sorting

3. Visualizing the DNA fingerprint

a. Transfer of DNA to nylon

b. Probing

c. DNA profile



1.Isolation of DNA
DNA must be recovered from the cells or tissues of the body. Only a small amount of tissue - like blood, hair, or skin - is needed. For example, the amount of DNA found at the root of one hair is usually sufficient.

2.Cutting, sizing, and sorting

Special enzymes called restriction enzymes are used to cut the DNA at specific places.
For example, an enzyme called EcoR1, found in bacteria, will cut DNA only when the sequence GAATTC occurs.


Sizing & Sorting
The DNA pieces are sorted according to size by a sieving technique called electrophoresis.
The DNA pieces are passed through a gel made from seaweed agarose (a jelly-like product made from seaweed). This technique is the biotechnology equivalent of screening sand through progressively finer mesh
 screens to determine particle sizes.


Is this similar to the chromatography that you have done earlier?
How is it similar and different?
Yes. It is similar to chromatography. Like chromatography, the difference in results is based on the solvent's molecular weight. However, they are different as chromatography is conducted on paper whereas Electrophoresis is conducted on agar for the solvent to move more easily and cover a greater distance.

3. Visualizing the DNA fingerprint
a. Transfer of DNA to nylon
The stained fragments of DNA do not last long in the soft gel. Investigator will carry out the next phase to “fix” the DNA fragment permanently for further investigation.

The distribution of DNA pieces is transferred to a nylon sheet by placing the sheet on the gel 
and soaking them overnight.

b. Probing
ADDING RADIOACTIVE PROBES
Adding radioactive or colored probes to the nylon sheet produces a pattern called the DNA fingerprint. Each probe typically sticks in only one or two specific places on the nylon sheet.

REMOVE PROBES
Excess probes are washed away leaving behind the unique DNA bands.

c. DNA 
profile
The final DNA fingerprint is built by using several probes (5-10 or more) simultaneously.
The radioactive DNA pattern is transferred to X-ray film by direct exposure.
The resultant visible pattern after development is the DNA FINGERPRINT

Wednesday, August 17, 2011

CSI Lesson 7(17/08/2011)

Spattered blood is defined as a random distribution of bloodstains that vary in size that may be produced by a variety of mechanisms. A spatter is created when sufficient force is available to overcome the surface tension of the blood.

The size, quantity and distribution of blood spatters depend on:
The quantity of blood subjected to impact,
The force of the impact and
The texture of the surface impacted by the blood

The identification and interpretation of spattered blood are significant for the following reasons:
Spattered blood may allow the determination of an area or location of origin of the blood source.
If found on a suspect's clothing, spattered blood may place that person at the scene of the altercation.
Spattered blood may allow the determination of the mechanism by which the pattern was created

Discussion :
The shape and size of the
depends on
• how much water you pour,
• how high you hold the stopper
and
• whether you're spilling it on
carpet, wood, linoleum or
some other surface.
A lot of water makes a larger
puddle.
If the water falls from a
distance, the puddle will be
smaller in diameter.
A hard surface will retain
more of a circular shape,
while carpet absorbs some of
the water and makes the
edges spread.


Surface Tension:
Blood, whether a single drop or large volume, is held together by strong cohesive molecular forces that produce surface tension within each drop and on the external surface. Surface tension is defined as the force that pulls the surface molecules of a liquid towards its interior, decreasing the surface area and causing the liquid to resist penetration.
The surface tension of blood is slightly less than that of water. To create splatters of blood, an external force must overcome the surface tension of the blood. In order to create smaller blood droplets or spatter from a volume of blood, this surface tension must be disturbed in some manner. Although a single drop of blood falling through air is affected by the forces of gravity and air resistance, these forces do not overcome the surface tension of the blood. No matter how far a drop of blood falls, it will not break into smaller droplets or spatters unless something disrupts the surface tension.
One factor in breaking the surface tension of blood is the physical nature of the target surface the drop strikes. Generally, a hard, smooth, nonporous surface such as clean glass or smooth tile, will create little if any spatter in contrast to a surface with a rough texture such as wood or concrete that can create a significant amount of spatter. Rough surfaces have protuberances that rupture the surface tension of the blood drop and produce spatter and irregularly shaped parent strains with spiny or serrated edges.
Viscosity:
Viscosity is defined as resistance to change of form or flow. The more viscous a fluid, the more slowly it flows. Blood is approximately six times more viscous than water and a density slightly higher than water. The SI unit for viscosity is the Pascal second and water has a viscosity of one.

Blood Droplets
The application of a force to a mass of blood causes the mass to break up into droplets. As a blood droplet travels through the air it retains a spherical shape due to surface tension. Smaller drops (1mm diameter and less) are almost perfect spheres while larger drops oscillate due a range of other forces acting on the droplet. [Smaller droplets do oscillate but the time required to dampen the oscillations is far less than larger droplets.] Droplets do not “break up” whilst in motion; another force would need to be applied to cause the droplets to further divide. The oscillations generally have no effect on the resulting spatter pattern except for instances where there are only a few stains and they are present on surfaces less than 100cm from the source.

Impact
When a droplet of blood strikes a horizontal surface at 90o it produces a circular stain. If the surface texture is smooth, such as glass or a polished tile, the surface tension will hold the droplet in the circular pattern. Essentially the surface influences the outflow. Surface tension ensures that the droplet collapses uniformly however the smooth surface means that the rim outflow is uniform. If the droplet falls onto a rough surface such as cardboard, carpet or concrete it will produce an irregular and distorted stain pattern. The rough surfaces results in an irregular rim outflow.

Phases of impact
There are 4 distinct phases of impact:
1) Contact /collapse
The droplet contacts the target surface and collapses from the bottom up. The part of the drop that has not yet collided with the surface remains as part of the sphere. As the collapse occurs, the blood that has come in contact with the surface is forced outward creating a rim. The rim gets bigger as more of the droplet comes in contact with the surface and more blood is forced into the rim.
The angle of impact affects the collapse as it defines the nature of the rim and the blood flow into it. For example: if the droplet impacts at 90o the blood flow into the rim is equal on all sides. If the impact angle is more acute, the blood flows into the area of the rim opposite the direction from which the droplet came.

2) Displacement
In this stage, the blood droplet has collapsed against the target surface and nearly all of the blood has moved from the centre of the droplet to the rim. The
actual area of displacement will be the same size as the eventual stain.
At the edge of the rim will be dimples or short spines. In this stage the movement of the blood is lateral or to the sides.
The surface texture is important. Surface tension is responsible for keeping the shape of the droplet as it moves through the air. When the droplet hits the
target surface, the ‘skin’ of the droplet, created by surface tension shifts its shape. The droplet doesn’t actually burst.
If the surface is rough, the blood flows irregularly into the rim so the spines or dimples that form will also be irregular in shape. This will result in a distorted or asymmetrical shape.

3) Dispersion
In this phase, most of the blood is forced into the rim. The spines and dimples continue to rise upward and in a direction opposite to the original momentum. As the amount of blood in the rim and spines increases they become unstable.

4) Retraction
The last phase results from the effect of surface tension attempting to pull the droplet back. If the forces trying to pull the droplet apart are overcome by
surface tension, the resulting stain will be reasonably circular and symmetrical in shape. If the forces pulling the droplet apart overcome the surface tension, the droplet will ‘burst’ and create an irregular stain pattern.
An excellent animation showing the impact behaviour of a blood droplet (November 2006).

Height
The higher the droplet falls from the ‘more’ blood satellite spatter occurs. Blood spatter is a broad term essentially meaning blood distributed through the air in the form of droplets. Satellite spatter, or spatter on the receiving surface may or may not be formed. If two similar sized droplets fall from different heights the resulting stains have different sizes. E.g. a droplet falling from 10cm will produce a different stain than a droplet falling from 100cm. The stain diameter from the 100cm height will be larger than the pattern from the 10cm height. The reason is that the velocity of the droplet will be greater the longer the droplet is airborne [until it reaches terminal velocity.] Above a fall distance of 2.2m there is little change in the diameter of the blood spot.

Force, Velocity and Droplet Size
The size and appearance of the bloodstains depends on the force that was used to create them. When an object comes into contact with blood, the force of the object moves the blood. The blood must respond to this energy transfer in some fashion. The response is often by the distribution of blood through the air in the form of droplets.
Velocity is measured in meters per second. At a crime scene there may be evidence of low, medium or high velocity blood spatter or a combination of these. For example, dripping blood (low velocity) has a velocity of 1.5 metres per second. Blood droplets produced from a bullet shot from a gun will have much greater energy and will travel faster.

Blood stain analysis-Velocity of blood splatter
Low velocity Blood Splatter:

-usually the result of dripping blood.
-The force of impact is five feet per second or less, and the size of the droplets is
somewhere between four and eight millimetres (0.16 to 0.31 inches).
• This type of blood spatter often occurs after a victim initially sustains an injury, not during the infliction of the injury itself.
• For example, if the victim is stabbed and then walks around bleeding, the resulting drops are a type of low-velocity spatters known as passive
spatters.

Medium velocity Blood Splatter:

• A medium-velocity spatter is one that had a force of anywhere from 5 to 100 feet
per second, and its diameter is usually no more than four millimetres.
• This type of spatter can be caused by a blunt object, such as a bat or an intense beating with a fist. It can also result from a stabbing.
• Unlike with a low-density spatter, when a victim is beaten or stabbed, arteries can be damaged If they're close to the skin, the victim bleeds faster and blood can spurt from wounds as his or her heart continues to pump. This results in a larger amount of blood and a very distinctive pattern. Analysts call this phenomenon projected blood.

High velocity Blood Splatter:

High-velocity spatters are usually caused by gunshot wounds, although they can be caused by other weapons if the assailant exerts an extreme amount of force.
• They travel more than 100feet per second and usually look like a fine spray of tiny
droplets, less than one millimetre in diameter.
• Bullet wounds are unique because they can have both back and front spatters, or
just back spatters.
• This depends on whether the bullet stopped after entering the victim's body or traveled through it. In most cases, the back spatter is much smaller than the front spatter because the spatter travels in the direction of the bullet.

Bloodstain pattern analysis can support other evidence and lead
investigators to seek additional clues.
After close analysis, blood spatters can indicate important
information such as:
• Type and velocity of
weapon
• Number of blows
• Handedness of assailant (assailants tend to strike with their dominant hand on the
opposite side of the victim's body)
• Position and movements of the victim and assailant during and after the attack
• Which wounds were inflicted first
• Type of injuries
• How long ago the crime was committed
• Whether death was immediate or delayed
• Blood spatters can lead to the recreation of a crime because of how blood behaves. Blood leaves the body as a liquid that follows the laws of motion and gravity. It travels in spherical drops due to surface tension. Blood molecules are very cohesive, or attracted to each other, so they squeeze against each other until they form a shape with the smallest area possible. These drops behave in predictable ways when they strike a surface or a force acts upon them. In the actual spatter analysis, a forensic investigator determines the trajectory of the blood (where the blood came from and how it spread over the surface). By measuring the shape of the bloodstain on a surface, the direction of movement can be determined. As well, the speed at which the blood contacted the surface can be approximated. This can help distinguish, for example, between the rapid movement of blood that can be produced by a gunshot or the severing of an artery in opposition to the slower movement of blood from
a minor cut.



Sunday, August 14, 2011

CSI Lesson Six (15/8/2011)

Evidence---possible location of DNA on the Evidence:
baseball bat or similar weapon--- handle, end ---sweat, skin, blood(NOTE: ONLY IN WBC-presence of nucleus), tissue

eyeglasses ---nose or ear pieces, lens ---sweat, skin

facial tissue, cotton swabs ---surface area ---skin cells

used cigarette ---cigarette butt ---saliva

stamp or envelope ---licked area ---saliva

blanket, pillow, sheet---surface area ---sweat, hair, urine(CELLS, DNA, SUGAR CONTENT-probably diabetic, chemicals can be found e.g. steroid), saliva

fingernail, partial fingernail---scrapings--- blood, sweat, tissue

WHERE ARE DNA SOURCES?
NUCLEUS IN CELLS.
***red blood cells do not have nuclei.

From Cells to Chromosomes to DNA & Traits
Each cell in our body contains a lot of DNA. In fact, if you pulled the DNA from a single human cell and stretched it out, it would be 3m long!
That’s about as long as a car!
How does all of DNA fit into a cell? The DNA is packaged into compact units called “chromosomes.”

How many chromosomes are there in each of our cell?
23 pairs.

What is DNA?
A nucleic acid that carries the genetic information in the cell and is capable of self-replication and synthesis of RNA. DNA consists of two long chains of nucleotides twisted into a double helix and joined by hydrogen bonds between the complementary bases adenine and thymine or cytosine and guanine. The sequence of nucleotides determines individual hereditary characteristics.

What is a gene?
A hereditary unit consisting of a sequence of DNA that occupies a specific location on a chromosome and determines a particular characteristic in an organism. Genes undergo mutation when their DNA sequence changes.

What is a chromosome?
A threadlike linear strand of DNA and associated proteins in the nucleus of eukaryotic cells that carries the genes and functions in the transmission of hereditary information.

What is hereditary?
Transmitted or capable of being transmitted genetically from parent to offspring

What is a gene?
A genetically determined characteristic or condition:

What is a trait?
A genetically determined characteristic or condition

DNA:
Where is DNA found in the human body?
Overview:
-From cells to chromosomes to DNa and traits
-Karotyping
-DNA extraction
-DNA fingerprinting

Understand Hereditary:
Our traits are the way we look, what we can do and sometimes what we are that we cannot see like blood type. Some of our traits can be changed whereas some cannot. Most traits that can’t be changed are inherited from our parents. These are called genetic traits. It is our genes, contained in our DNA, that determine the traits. Some traits can be changed, like hair colour, as they are determined by what we do and how we live, i.e. by our environment. However there are also traits that are affected by both our genetics and the environment, such as weight and height.





Tuesday, August 2, 2011

CSI Lesson Two (3/8/2011)

Blood Splatter:
-Pattern left behind by falling or projected drops of blood can help investigators ro determine how and where the crime was committed. Therefore, blood drops and stains are usually examined closely before the evidence is collected. There is lots of physics (kinematics) behind it.
Look at the various blood splatters below and guess how they are formed.
Blood Splatter ONE:


Blood Splatter TWO:


Blood Splatter THREE:


Blood Splatter FOUR:


Blood Splatter Pattern from a Laboratory Experiment by Mr Leong TK & Chua HL

Answer the following questions in your journal:
1. What is the shape of blood splatter?
Blood splatter is round. Blood splatters vary in degree of "ovalness", sometimes being elongated.
2. Describe any other characteristic of the splatter.
Blood splatter is most concentrated at the centre of splatter, making it darker when dried. Blood splatter also does not have smooth sides but rather jagged edges.
3. What are the factors that affect the shape of the blood splatter? Name as many as possible.
-Angle of elevation
-Distant from its origin and the surface
-Surface of which the blood dropped on
-Force--> which in turn affects velocity of the blood
4. Generate some hypothesis from the blood splatter patterns observed above.
-The higher the angle of elevation, the longer the blood splatter.
-The higher the angle of elevation, the narrower and elongated the blood splatter.
-The further the distance from the origin and surface of which the blood was dropped on, the bigger the diameter of the blood splatter.
Blood Splatter Experiment:
Conducting the experiment


Our results



Raw data of Blood splatter experiment:
Height at which blood is dripped from(10cm, 30cm, 60cm, 100cm, 150cm)
A10: 0.9cm

B10: 1.1cm

A30:1.0cm

B30: 1.1cm

A60: 1.1cm

B60:1.2cm

A100: 1.2cm

B100: 1.2cm

A150: 1.3cm

B150: 1.4cm




Angle of elevation (10,30,50,70,100 degrees)

P10: 1.1cm

Q10: 1.2cm

P30: 1.2cm

Q30: 1.3cm

P50: 1.3cm

Q50: 1.3cm

P70: 1.2cm

Q70: 1.2cm

P100: 1.3cm

Q100: 1.3cm

Blood splatter Activity(spraying paint on bucher sheets):




Thursday, July 21, 2011

CSI Lesson Two (22/7/2011)

Fingerprint patterns in Class:
Class Class Index Number Your fingerprint pattern
210 9 loops
210 4 loops
210 10 loops
210 2 arches
210 24 whorls
210 28 whorls
210 27 whorls
210 15 loops
210 29 loops
213 27 whorls
213 17 whorls
213 7 whorls
213 15 loops
213 20 loops
213 26 loops
213 30 loops
213 32 arches
213 25 loops
213 24 loops
213 23 arches
213 31 whorls
213 16 whorls
213 13 whorls
213 21 whorls
213 4 arches
213 29 loops
213 2 whorls
213 14 arches
213 19 arches
213 22 loops
213 6 loops
213 10 loops
213 3 loops
213 33 loops
213 18 loops
213 28 loops
210 18 whorls
210 19 loops
210 17 whorls
210 3 whorls
210 21 whorls
210 8 loops
210 25 loops
210 6 loops
210 10 whorls
210 30 loops
210 25 loops
210 1 loops
210 16 loops
210 20 whorls
210 31 whorls
210 6 loops
210 32 whorls
210 5 loops
210 13 loops
210 7 loops
210 11 whorls
210 26 loops
210 12 whorls
210 23 whorls
213 1 loops



No. of students
Patterns 210 213
Arches 1 5
Whorls 14 8
Loops 18 15


Percentage of students

Patterns 210 213
Arches 3% 18%
Whorls 42% 29%
Loops 55% 54%

CSI Fingerprinting Answers to Questions:
Ridges and Pores Activity
Q)Where are the pores found? Are they regularly spaced?
A)They are found on the ridges of fingerprints. Yes, they are regularly spaced.

Cyanoacrylate(Superglue) Fuming Method
Q)If the contrast of the white against the black background is still too faint for a good detailed photograph to be captured, what could be done to enhance the fingerprint?
A)Dye the fingerprint with fuorescent substance to make it glow in UV light.

Iodine Fuming Method
Q)What are the possible substances that may be used to render the prints more permanent?
A)

Powder Dusting Method
Q)What is the magnetic powder dusting and how does it work?

Sunday, July 17, 2011

CSI Lesson One (18/7/2011)

Slylock observed:
-type of trash
-bull is herbivore--> thus only can eat plants.
-racoon is omnivore-->can eat both plants and animals
-thus, racoon is the trash thrower.

Activity Two Reflection:
First time, I did not see the moonwalking bear as i was concentrating on the number of passes that the white team made.
However, during the second time, I ignored the passes and saw the moonwalking bear.

Activity Three:
Different types of physical evidence:
Hair, Fibre, Footprints, Scratch prints, Wound, Letter, Fingerprint, Blood stain, WOund, Paint chips.

Fields:
Pathology, Forensic sciences, coroner, Ballistic

Evidence and Clues found:
Used a blade, strong enough to pierce into the heart
Used a crowbar to break into the house
Murderer drags his feet
Fingerprint matched the male murder suspect (the electrician, Patrick Murray)
Match the type of paper the woman used to check whether she visited the store. Ask workers there whether they recognise her. Woman is also environmentally friendly.
suspect has to be 5'9" tall and check whether he has a criminal record or self defence background
Time of death 10.30pm and check for alibi
Paint Chips-check whether it can be found on the suspect's body or on the tool.

Conclusion:
The electrician, Patrick Murray, is the murderer because Mr. Hughes died at 10.30pm and the electrician was seen walking back and froth Mr. Hughes property at 10.15pm. The other two women came at 1pm and 4pm. Also, his fingerprint was found on the broken vas