12th lesson CSI- Identity 2- Karyotype

Today, we learnt more about chromosomes and most importantly about karyotyping.

We started the lesson with a revision on DNA and chromosomes.

What is DNA?

DNA is the instructions for the cell's function, which is located in the nucleus.

DNA encodes detailed set of plans. JUST LIKE BLUEPRINTS :)

DNA- Sugar phosphate backbone
- The four bases: A, T, C, G
- Hydrogen bonds that bond the bases together as much as possible to form 3 dimensional helix bridge

DNA strand made of letters-> letters make words-> words make "sentences" -> genes, which tell cells to make other molecules such as proteins.

What is gene? 

Genes: instruction manuals for our bodies, directions for building all the proteins that make our bodies function.

For eg: Haemoglobin gene
- If it's normal, then the protein works fine

The difference! 

- But if the gene is "mutated", changes in haemoglobin protein such as "sickle cell anemia"

For eg: Enzymes that produce pigment in our eyes and keratin that make our hair/ nails grow.

What is chromosome?

structure of chromosome :)

- It is the storage for DNA
Firstly, the double helix of DNA is formed.
Then the DNA is wrapped around proteins.
Lastly the proteins are packed to form chromosomes.

Most of us get 46 chromosomes. XX-> girl XY-> boy

Not all organisms have the same no. of chromosomes. For eg: humans= 46, onions= 16, mosquitoes=6, carp=104

HOW TO IDENTIFY CHROMOSOMES? 

- SIZE
- BANDING PATTERN (location of giemsa bands on chromosomes make each chromosome pair unique)
- CENTROMERE (position of it)

Karyotype-

a karyotype :)

An organised profile of a person's chromosomes. They are arranged and numbered by size, from largest to smallest. This helps to quickly identify the chromosomal alterations that may result in a genetic disorder.

How to do this?
Scientists take picture of someone's chromosomes, cut them out and match them up using size, banding pattern and centrometre position as guides.

We did this based on two sheets of chromosomes given to us and we cut out each chromosome. Then, we arranged them in order and tried to find out the chromosomal alterations to find out which syndrome the person has and if he/ she actually has a syndrome.

This is the process of how the karyotype is prepared:

the process ! gah it's blurred :(

1.) Blood culture is centrifuged to separate the blood cells from the culture fluid
2.) The fluid is discarded and a hypotonic solution is mixed with the cells. This makes the red blood cells swell and burst. The white blood cells swell but do not burst and their chromosomes spread out.
3.) Another centrifugation step separates the swollen white blood cells. The fluid containing the remnants of the rbc is poured off. A fixative is mixed with the white blood cells. A drop of the cell suspension is spread on a microscope slide, dried and stained.
4.) The slide is viewed with a microscope and images of the metaphase chromosomes are sorted by size and shape on a computer.
5.) The resulting display is the karyotype.

I have researched on some syndromes caused by chromosomal alterations:

1.) Trisomy 13- Patau Syndrome
- Not inherited
- Presence of 3 chromosome 13s in all cells
- Occurs 1 in 10000

*Trisomy 13 mosaicism- presence of an extra chromosome 13 in SOME cells
*Partial Trisomy 13- presence of an extra chromosome 13 in the cells

Symptoms:

Cleft Lip

Clenched hands

- Close set eyes

- Decreased muscle tone

- Extra finger/ toes 

- Hernias (bulge in an organ) 

- Hole, split, cleft in iris (coloboma) (Blurred vision, ghost image, can't see things clearly)

- Low-set ears 

- Scalp defects 

- Seizure

- Single palmar crease (indicate problems with development)

- Skeletal abnormalities

- Small eyes

- Small head 

- Small lower jaw

- Undescended testicle

MEDICAL PROBLEMS: congenital heart disease-> abnormal placement of heart to right side instead of left

2.) Trisomy 18- Edwards Syndrome 

- Extra chromosome 18 

- Occur in 1 in 3000 live births

- Most Edwards Syndrome babies die before birth

Symptoms: 

- Nervous system and brain-> mental retardation, delayed development, high muscle tone (rigid in the limbs, delayed gross and fine motor skill development, stiff legs have difficulty relaxing muslces), seizures, physical malformations (brain defects)

-Head and face-> small head, small eyes, wide-set eyes, small lower jaw, heart: congenital heart defects, bones: severe growth retardation, clenched hands with 2nd/ 5th fingers on top of others, hands and feet defects, malformations of digestive tract, urinary tract and genitals. 

3.) Trisomy 21- Down Syndrome 

- Extra chromosome 21

Physical defects: flat face profile, upward slant to eyes, small ears and protruding tongue 

'

Hypotonia- "floppy"-> tend to reach developmental milestones: "sitting up", "crawling", etc. slowly. 

Digestive issues, problems with feeding, dressing and toilet teaching. 

Medical problems:

- Increased risk of pulmonary hypertension: irreversible damage to lungs

- Problems with hearing + vision (cataracts, structural problems, fluid buildup in inner ear, cross eyed, near sightedness or farsightedness 

- Thyroid problems

- Intestinal abnormalities

- Seizures

- Respiratory problems

- Obesity

- Higher vulnerability to infection

- Higher risk of childhood leukemia  

This is a video intro to karyotype:)

11th Lesson- CSI DNA Identity 1

For today's lesson, we learnt about DNA and traits.

Key takeaways: 

- Most traits can't be changed -> genetic traits

- Some traits can be changed -> influenced by environment (for eg: hair colour as it can be dyed)

With the worksheet given, we assessed ourselves for some characteristics:

RH/LH	Right / Left handedness
A/a	tongue rolling
B/b	widow's peak
C/c	cheek dimple
D/d	free earlobe
E/e	curly hair

Next, we were to plot our results on the individuality chart and i found out that i was a 32e. 

In our class, there were alot of "32e". 

I was quite amazed as i did not expect everyone to be any similar at all, i guess i was wrong. From this exercise, i learnt alot because even though many of us have certain similar traits, we still look different because of our DNA.

*Moreover, i have made some assumptions beforehand (that are probably misconceptions now that i know) I thought that if we really could find someone with the same individuality number as me, that person would be my good friend or someone who had a very similar personality with me. However, i was wrong. Having similar traits does not mean that we would be exactly similar to the person. We may look totally different and behave in totally different ways. After this exercise, it cleared the question in my brain: "Would i have the same personality as someone with the same individuality number as me?" *


A graph of the traits were then collated and shown below:

The following are some of the traits i researched abit more on :) (since these are the common traits)

1.) Based on the slides went through, earlobes that hang free are detached earlobes. Earlobes that are directly attached to the side of the head are attached earlobes.
Apparently, some scientists have reported that this trait is due to a single gene for which unattached earlobes is dominant and attached earlobes is recessive. Other scientists have reported that this trait is probably due to several genes.

*However, i feel that it is sometimes hard to tell whether some people have attached or detached earlobes as personally, mine is exactly halfway between the two extremes. Thus, i am not sure whether to select yes or no for attached earlobes trait as for my earlobe, it looks as if it's detached due to a line between my ear and the skin but then up close, it actually looks attached. My earlobe isn't exactly very detached, nor isit very obviously attached. As all my life i've thought my earlobe was attached, i selected the attached earlobe option and i've only realised now that my earlobe trait is quite unclear...*

Different earlobes of cyclists :) From most detached to most attached left to right continuously for both rows!

2.) Tongue rolling ability may be due to a single gene with the ability to roll the tongue a dominant trait and the lack of tongue rolling ability a recessive trait.

CAN ROLL! 

CANNOT ROLL! 

*For me, when i was younger, like about primary 1 or 2, i couldn't roll my tongue, i practised rolling my tongue for a week and even tried to squeeze both sides of my tongue together but it still wouldn't work. However, when i went up to P4, i suddenly found out that i could roll my tongue. I haven't been practising and was quite shocked that i actually could perform this tongue rolling trick thing. xD
My question is: Is it possible that someone may be born with the tongue rolling ability but is unable to do so in her earlier stages of development or youth, but this trait only develops in the person when she grows older?*

Research has been done in 1950's and 1970's and it showed that identical twins don't always share the ability to roll their tongues.

This is because we may have the gene for a certain trait but not see any sign of it. And there is a number of reasons why we can't see the sign of that gene even though we possess it.

One reason is trigger from the environment.

I would use the analogy of juvenile diabetes to explain this reason.
There are genes that make people more likely to get this form of diabetes, But to get juvenile diabetes, there needs to be a viral infection. If you have juvenile diabetes gene(s), then the part of your pancreas that makes insulin looks a bit like a certain virus. When the virus infects you, your body mounts an attack on the virus, destroying it. Unfortunately, in a "friendly fire" incident, part of your pancreas is also destroyed and you get juvenile diabetes.

juvenile diabetes- in the pancreas

Someone never infected with the virus but who has the gene (s) for juvenile diabestes will not get this form of diabetes. But they can pass the gene(s) onto their kids. And if the child gets infected with the virus, then he or she can develop diabetes. Perhaps tongue rolling also needs some sort of environmental trigger even though it probably isn't virally related.

Another reason is not having enough of the gene. That means you need two or more different genes to see a trait and you only have one. For example: At its most basic, there are two eye colour genes, a brown-blue one called bey2 and a green-blue one called gey.

may be a combination of 

To get blue eyes, both of your bey2 and both of your gey genes need to be the blue kind. For example, if both your bey2 are blue but one of your gey is green, then you have green eyes. So to get blue eyes, both genes need  to be "right."

*Two genes, bey2 and gey, work together to make brown, green or blue eyes. Each gene comes in two versions or alleles. One form of bey2 makes of melanin-> B. The other form makes only little->b.One form of gey makes some melanin-> G. While the other makes only a little-> b.
B- brown eyes
G but no B- green eyes
only b- blue eyes.
THIS IS A TABLE OF THE COMBINATION:
*

Now imagine that to be able to roll your tongue you need two genes, A and B. For each of these genes, there is a certain dominant version that lets you roll your tongue. Now let's say that one parent has a dominant A and the other parent has a dominant B. Neither parents can roll their tongues. If one parent passed on a dominant A and the other a dominant to their child, there would be a child that could roll her tongue. Parents who cannot roll their tongue would then have a tongue roller for a child.

Another example is something called a modifier gene. A modifier gene can turn another gene on or off. For a gene to have an effect, it must be "on". On means that the instructions in the gene have been made into a protein that can do something useful.
Genes are just instructions for making proteins. They don't do anything on their own. The tongue-roller gene has to make a protein that allows the muscles of the tongue to bend in a certain way. Now imagine another gene that keeps the tongue-rolling protein from being made. We name it M. M could eliminate the tongue rolling protein in lots of different ways. For example, M could prevent the cell from reading the instructions in the tongue-rolling gene or destroy the tongue-rolling protein outright.

Thus, you can't roll your tongue because M has gotten rid of the tongue rolling protein.
If two of these people have kids and they pass on the tongue rolling gene but not M, these children would then be able to roll their tongues.

THus there are potentially alot of ways for nonrollers to have roller children. Even "simple" traits liek tongue rolling can get quite complicated!

3.) Based on my research, dimples are actually genetic defects caused by shortened facial muscles. Transfer of dimples from parents to children occurs due to just one gene. The dimple creating genes are present in the sex cells prior to the process of reproduction. Each parent provides one of these genes to the child. So, if both the parents have dimples, the children have 50-100% chances of inheriting dimple genes.

dimple

no dimple

Sometimes, a variation in penetrance may also occur. Some individuals may carry a particular gene, but they do not manifest the traits associated with it. However, they still pass on the traits to their successive generations.

Apart from variable penetrance, there may also be reduced penetrance which allows a generation to skip having dimples, although they may appear in subsequent generations.
This occurs when one person inherits certain genetic trait along with another trait that suppresses it. For example, a person may inherit genes for dimples and also other genes for small face. In this case the small face will not allow the gene for dimples to function. Such people are called passive carriers of dimple genes.

10th lesson- DNA fingerprinting

For this lesson, we learnt about a very important part of forensic science, which is DNA FINGERPRINTING.

Basically, we learnt many complex ideas that we never really learnt before... like what DNA was made up of. DNA= Double helix :)

The sides/ backbone of the DNA molecule are made up of sugar (DEOXYRIBOSE) and phosphate molecules.
The rungs in the middle are made up of pairs of nucleotides or nitrogen bases. A-> T and G-> C (vice versa) A= adenine. T=Thymine. G=Guanine. C=Cytosine.
Importantly, the order of the bases determines the genetic code.

The sides or backbone of the DNA molecule are made up of sugar (deoxyribose) and phosphate molecules.
The rungs that form the middle of the molecule are made up of pairs of nucleotides or nitrogen bases.
Adenine pairs with Thymine (A with T) and Guanine pairs with Cytosine (G with C)
The order of the bases determine the genetic code.

DNA structure

DNA fingerprinting is a test to identify and evaluate the genetic information in a person's cells. 

It is called a "fingerprint" because it is very unlikely that any 2 people would have exactly same DNA information, in the same way that it is very unlikely that any 2 people would have exactly same physical fingerprint. 

It is used to determine whether a family relationship exists between two people, to identify organisms causing a disease, and to solve crimes. 

Only a small sample of cells is needed for DNA fingerprinting. A drop of blood or the root of a hair contains enough DNA for testing. Semen, hair or skin scrapings are often used in criminal investigation. 

The first step in DNA fingerprinting is to break open the sample cells and collect the DNA. Next many copies of the DNA are made using polymerase chain reaction (PCR). 

To get the DNA fingerprint: 

1.) All of the DNA is broken into pieces at certain locations by restriction enzymes that break each DNA strand at the same place.

2.) The DNA pieces are placed at the top of a special gel held in a frame. 

3.) AN electric current is applied to the gel. The current separates the DNA into bands of identical pieces. This process is called gel electrophoresis. 

4.) The band pattern is transferred to a nylon membrane containing a radioactive chemical. The chemical makes the bands show up clearly. 

For a criminal investigation, photos of the criminal and suspect DNA are compared. The results as shown in the figure above show that the suspect is not the criminal. 

Further detail on gel electrophoresis...

Illustrated process of gel electrophoresis

1.) A gel is prepared by pouring a liquid containing either melted agarose or unpolymerized acrylamide between two glass plates a few millimetres apart. 

2.) As the agarose solidifies or the acrylamide polymerises into polyacrylamide, a gel matrix (orange ovals) forms, consisting of long, tangled chains of polymers. 

3.) The dimensions of the interconnecting channels, or pores, depend on the concentration of the agarose gels than in polyacrylamide gels, the former are used to separate large DNA fragments (around 500 bp to 20 bp) and the latter to separate small DNA fragments (1 nucleotide to around 2 kb) 

4.) The mixture of DNA fragments to be separated is layered in a well at the top of the gel and an electric current is passed through the gel. 

5.) DNA fragments move toward the positive pole at a rate inversely proportional to the log of their length, forming bands that can be visualised by autoradiography (if the fragments are radiolabeled) or by addition of a fluorescent dye such an ethidium. 

9th Lesson- Handwriting Analysis!

Today's lesson was about handwriting analysis. :)

We were given 3 pieces of paper.
On the first piece of paper, we wrote a paragraph of words in our normal handwriting with our names labelled on it.
On the second piece of paper, we wrote the same paragraph of words in our normal handwriting WITHOUT labelling it with our names.
On the third piece of paper, we were to disguise our handwriting by writing the same paragraph more differently WITHOUT labelling it with out names.
Our teacher then swapped the second and third pieces of paper of our group with another group and see if they can match the disguised handwritings of each person to each piece of paper which has the undisguised handwriting. :)

It was a fun experience as we could get a deeper understanding of what our classmates' handwritings were like and i never actually noticed some of the small and significant details when they write certain characters. 

We learnt that handwriting analysis is used in CSI to determine whether forgery has been committed or identify the author of writing samples. Forgery is most common on cheques and therefore, handwriting analysis will reveal any forgeries being made. Moreover, people have personal habits in their handwriting that make it unique. It is possible to disguise our handwriting but experts can still eventually tell if the characters/ words were written by the same person!

No two handwritings can be the same!

Handwritings are class characteristics.

*What are class characteristics?*

Class characteristics are opposite of individualisation. The process of classification of evidence is a process of assigning it to these groups or categories. Members of a given class will share the same class characteristics, whereas evidence that can be individualised will possess characteristics that make it unique.
Class characteristics are not enough to individualise the sample or link it to one individual. Handwriting has distinctive class characters. For example: to write a capital A, two slanted lines meet at a point and are linked by a horizontal line about half way up, conversely, a Q involves a circular stroke. However, everyone writes letters in various ways, imparting individual characteristics. Almost every type of physical evidence can be classified in some way, but not all evidence can be individualised.
***
An investigator would request for a handwriting specimen to compare with the questionable document.
The collected writing are samples done before investigation and these include: applications, work documents, previous checks, etc!

We gained knowledge about the different characteristics for comparing handwriting.

1.) Line quality: do letters flow smoothly or written with very intent strokes?
2.) Spacing of words and letters + margins
3.) Ratio of height, width and size of letters: Are they consistent in all aspects?
4.) Lifting pen: Does author lift his or her pen to stop writing word/ start a new word?
5.) Connecting strokes: In what ways are the capital letters connected to lower-case letters?
6.) Unusual letter formation: Are any letters written with unusual slants/ angles?
7.) Pen pressure!
8.) Slant?
9.) Baseline habits! straight or uneven?
10.) Fancy writing habits? curls loops unique styles?
11.) Placement of diacritics: How does the author cross the t's or dot the i's.

AFTER THIS LESSON, i gained ALOT OF INTERESTING KNOWLEDGE. At first when i saw the title, i thought handwriting analysis would be about interpreting someone's personality and character just by looking at the handwriting. However, handwriting analysis in CSI and forensic science is MUCH more complicated, detailed and logical, allowing interpretations to be made sensibly and logically. :) -> helps to find out if there're any forgeries,etc!!!

8th CSI Lesson: BLOOD SPLATTER

This CSI lesson was another lesson about blood splatter. However, this time, we got to create our own crime scene using different liquids with different colours.

The toilet in our school has be transformed into a crime scene and we were given 5 different tubes of liquids with different colours. They were all in colours of pink, green, yellow, sky blue and cobalt blue. We were to make use of the blood splatter patterns and concepts we learnt in our previous lesson to create a crime scene and let our classmates analyse what exactly happened while the crime was taking place.

Firstly, we set up OUR group's crime scene near the sink and the mirror. This was the situation:
1.) A girl was in the toilet, standing in front of the mirror and sink grooming herself.
2.) She was oblivious to the fact that danger was lurking and a psycho killer was lurking around the corner.
3.) The psycho corner stepped into the toilet and started pacing towards her with a knife behind his back.
4.) The girl heard the guy's footsteps coming and she turns to her right and is shocked to see the guy.
5.) The guy advances towards her, whips out a knife from the back and slashes her from his right to his left in an upwards motion.
6.) Girl hurls body in the direction of the sink and mirror and kneels down on her knees due to immense pain, palms clutch onto wound due to great pain and then palms clutch onto the sink for support.
7.) Wound's blood smudges against the sink while girl kneels onto ground and thus smudges are created at the front of the sink.
8.) Wound's blood drips down tremendously causing a pool of blood to be gathered onto the ground.
9.) Slash blood splatter seen on sink and mirror.

Next, the OTHER group set up their crime scene and we were given the task to analyse the scene. This was what we came up with:
1.) Firstly, we think that the murderer grabbed the victim by the head and slammed her head into the wall, causing a big patch of blood to be formed on the wall, with blood dripping down to the ground.
2.) Then, the murderer grabbed the victim by the head once more and slammer her head into the wall, causing another big patch of blood to be formed on the wall, with blood ALSO dripping down to the ground. (initially, we thought that there may be another person involved since the blood colours used for the 2 blood splatters are different (yellow and blue), however we could not find any possible explanation for the other blood splatters present which indicated that there were 2 people injured, thus, we scraped the idea that 2 people were involved in the crime.)
3.) Judging by the position of the two blood splatters (for the head slams), we conclude that the victim was probably a short and petite person (most likely a girl) because the height of the blood splatter for the head slams was at a low height from the ground, probably around 1.4m.
4.) The girl was semiconscious and thus fell down and sat on the floor with a pool of blood on the ground.
5.) There were a few smudges around the pool of blood, indicating that the girl attempted to stand up to escape/ fight back. Especially since from the front there were two smudges pointing outwards, which may be caused by the legs of the victim.

Then they revealed the actual scenario to us!
1.) The guy got raped by the girl and out of anger, violence, the guy grabs and slams the girl's head into the wall. He slams the girl's head once more creating two blood splatters.
2.) Girl becomes unconscious and falls to the ground, the pool of blood is gathered on the ground from the blood dripping from the wall.

Using the concepts we learnt, the angle and direction of impact, the height of impact of the blood, the velocity of the impact and surface of impact, we interpreted the whole situation and matched our analysis to the actual scenario. For our group, it was mainly involving the observation of the shape of the blood pool and the direction at which the blood flows to. There was also blood dripping on blood, which indicates excess bleeding and a serious injury being sustained-> head injury. The small little blood splatters around the big patch of blood on the wall also indicates that the impact was huge and thus the force exerted by the murdered when slamming the victim's head against the wall, was large too.

PHOTOS + VIDEOS:

The blood splatters our group made :) Slash blood splatter, handprint and smudge marks are on the upper mahjong paper while the dripping blood is on the lower mahjong paper. 

Slash blood splatter and handprint. Smudge mark of the wound can be seen at the lower part of the mahjong paper. 

The dripping blood from the wound.

Dripping blood from the wound up close.

The bloody handprint made on the sink after clutching onto bloody wound. 

Slash blood splatter, handprints, and smudge marks :) 

An example of how we described our scenario to the class on foolscap through depictions :P 

 These are videos of us re-enacting the scenes... May not be very scientific but just for entertainment :)

Seventh CSI Lesson: Blood Identification

Blood identification is very essential in crime scene investigation as it helps to identify and match the blood samples with the different suspects, culprits and victimes, thus providing more information to the police for them to crack and solve the case.

Firstly, the context was set:
A man was murdered in the loading bay of a dance club and at the crime scene there were red stains all over: bottles of chili sauce, tomato sauce, fruit juice and dyes. The police were unable to identify which were the blood stains and thus had to bring back all the samples of these stains for blood identification.

There are simple tests used to identify blood:
1.) Add benzidine to a solution made from dried blood and water. The solution turns blue or in the case of luminol, glow in the dark! :) In the lab, we used luminol.

Basic idea of luminol: reveal traces of blood with light-producing chemical reaction between several chemicals and hemoglobin in the blood. The molecules break down and the atoms rearrange to form different molecules. In this reaction, the original molecules have more energy than the products (the resulting molecules). The molecules get rid of the extra energy in the form of visible light photons. This process, is generally known as chemiluminescence, which is the same phenomenon that makes fireflies and light sticks glow.

2.) Kastle-Meyer test uses a substance called phenolphthalein, which is normally colourless, but turns pink in the presence of blood.

Usually, this is how the test is carried out.
A drop of phenolphthalin reagent is added to the sample, and after a few seconds, a drop of hydrogen peroxide is applied to the swab. Sometimes the swab is first treated with a drop of ethanol in order to break open the cells that are present, resulting in increased sensitivity and specificity. This test is nondestructive to the sample, which can then be kept and used in further tests at the lab, such as in DNA analysis. If the swab turns pink right away, it is said to test positive for blood.

However, this test result is presumptive positive. In other words, it is not a conclusive test for blood. Other analyses would be carried out to confirm the presence of blood. This is one thing to note: waiting for a period of time over 30 seconds will result in most swabs turning pink naturaly as they oxidise on their own in the air. Some chemicals and biological fluids that DO NOT contain blood can also cause the colour change. Thus, these substances have to be avoided because they produce false positive results= positive result (colour change) in ABSENCE of blood.

How does this test work?
The Kastle-Meyer test relies on the iron in hemoglobin in the blood to promote the oxidation of phenolphthalin to phenolphthalein. phenolphTHALIN is colourless, but in the presence of blood and hydrogen peroxide, it changes to phenolphTHALEIN, which makes the solution pink.

3.) Add hydrogen peroxide to the blood sample. It will bubble profusely.

Why does it foam/ bubble profusely?
Blood and cells contain an enzyme called catalase. Since a cut or scrape contains both blood and damaged cells, there is lots of catalase present. When the catalase comes in contact with hydrogen peroxide, it turns the hydrogen peroxide into water and oxygen gas.

Catalase does this extremely efficiently-- up to 200 000 reactions per second :O The bubbles seen in the foam are pure oxygen bubbles being created by the catalase. Putting a little hydrogen peroxide on a cut potato will also achieve the same result because catalase in the damaged potato cells reacts with the hydrogen peroxide. Hydrogen peroxide does not foam in the bottle or on skin because there is no catalase to help the reaction to occur. It is stable at room temperature.

We were given 6 different samples to test for blood. Firstly, before we carried out the blood detection test for the first test, we had to fill in our predictions for the samples. After which, we carried out our results and these were our results:

Table of results for first test :) 

The samples tested positive for catalase: 4, 5 and 6

Next, we proceeded onto test 2 using the samples tested positive in the previous test. We were given filter papers and luminol spray. We dripped 2 drops onto filter papers for each sample. Then we placed the filter paper in the open cupboard of our lab bench, where it is darker and we sprayed luminol onto the filter paper. The bluish glow was then observed.

Samples that glow/s in the luminol test: 4 and 5.

Following that, the third test was used to test for the presence of blood for the samples that glowed in the previous test. We were again given filter papers and this time, the Kastle-Meyer Reagent also. We dripped 2 drops of samples onto filter papers individually and 4 drops of Kastle-Meyer Reagent onto each filter paper for each sample. Then, we had to wait 3 minutes and record our observation. After waiting to ensure that no colour develops at this stage (because there may be other external factors that cause the colour change), add two drops of 3% hydrogen peroxide. An intense pink colour is positive test for peroxidise activity, indicative of hemoglobin and thus, blood.

OBSERVATION: SAMPLE 4 TURNED INTENSE PINK :)
sample5 only turned a very light pink!

CONCLUSION: SAMPLE 4 IS BLOOD!!!
sample 5 had a colour change maybe due to other factors such as the presence of other chemicals/ oxidisation that causes the light pink colour to be obtained.

PHOTOS:

Lots of bubbling in sample 4 on the right. Small amount of bubbling in sample 5 on the left :) 

Sample 4 glowing in the dark after luminol was sprayed :)

Reduced phenophthalein! 

Sample 5- light pink! 

QUESTIONS:
Why is it necessary to use more than one test to determine whether the given stain is blood?
These tests are presumptive tests. We cannot conclude directly and accurately based on only just 1 test but we can eliminate the other samples to obtain the final sample that is BLOOD. For example: test 2 is a presumptive test, we would need to carry out other analyses to confirm the presence of blood.

Once you know that a stain is real blood, what else would you do as a forensic scientist?
I would carry out a DNA test to test if the blood matches with suspects or victims. I would also check if it is human/ animal blood.

 With these tests to detect presence of blood, it would be very useful to the forensic scientists as they are able to carry out blood comparison analysis, etc. and aid in progress of the police's work in crime scene investigation.

Sixth CSI Lesson: Blood Splatter!

In this lesson, we learnt about blood splatter. We learnt that the pattern left by falling or projected drops of blood can help investigators determine where and how a crime took place. Thus, it is important to examine the blood drops and stains closely and detailedly.

Firstly, we learnt about height of impact. As a drop of blood falls through the air, it accelerates and theoretically, the greater the height, the greater the speed of the blood upon impact, and hence the larger the diameter of the blood stain.
This is the equation to calculate vertical distance travelled by the blood
s= ut + 1/2 at^2
s= vertical distance travelled by the blood
u= initial speed of the blood
a= acceleration due to free fall (9.8ms^-2)
t= time taken for the blood to reach the point of impact

Firstly we carried out the first experiment to see if the vertical distance really does affect the diameter of the blood stains obtained. We attached an A4 sized paper onto the clipboard and placed it on a surface. Then, we clamped the dropper to the retort stand 10 cm above the paper on the clipboard.
Next, squeeze a drop of blood to the paper below and measure the diameter of the blood drop. Repeat this to obtain 2 results and from there get the average diameter. Repeat the above steps for vertical distances: 30, 60, 100 and 150. Following that, record results in table form.

Our results showed that the greater the vertical distance, the greater the diameter of the blood stain. These were our results:

Table of results 

Then, we had to carry out a second experiment which was regarding the angle and direction of impact of the blood stains. We were first given some information on the angle and direction of impact in the worksheet.

Angle of impact- acute angle that is formed between the direction of the blood drop and the surface it strikes-> this is used to determine the area of convergence and area of origin.
ANGLE OF IMPACT (on flat surface) CAN BE CALCULATED BY MEASURING LENGTH AND WIDTH OF STAIN.
For example: when a droplet of blood falls to the surface at 90 degrees, bloodstain will be circular and it will be more elliptical when angle of impact increases.
elliptical- egg-shaped, rounded like an egg :0 haha.

Calculation of angle of impact:
i= sin^-1 W/L

We had to take some precautions before carrying out the experiment. For example: we had to take note that when measuring the length, L and the width, W of a stain, no part of hte spines, tails or satellite splatter are included in the measure.

Firstly, we attached A4 paper to the clipboard and placed it on the floor. Then clamp the dropper to the retort stand and place it at least 100cm above the surface of the paper. Elevate the clipboard to 10 degrees and squeeze one drop of blood onto the paper. Then, measure and record length and width. (Don't forget to label the stain- miss siow always emphasises HAHA) Repeat these steps for the other angles: 40 and 70 degrees.

Based on our results, we have concluded that the higher the angle of elevation, the lesser the angle of impact.

There were also other knowledge gained such as the velocity of impact of the blood and the surface of impact of the blood. Blood that drops on a smooth surface (smooth edges) would look different from blood that drops on a rough surface (more jagged edges)

Overall, i felt that this was quite a useful and beneficial session of CSI because i never knew that the way the blood stains were positioned or how they looked like could tell us so much about what happened at the crime scene. It gave me a more insightful outlook to this topic about blood splatter in the CSI module and it urges me to learn more as i believe that as mentioned in the first lesson, physical evidence speak alot and besides blood splatters, there may also be other evidences that can give us more in-depth and wider vision of the case such as gunshots in human bodies, or post-death changes in the dead bodies after the crime was committed.

PHOTOS:

Measuring the vertical distance 

The blood given to us 

Our blood splatters :)