CSI Lesson 9 (19/8/11)

Today, we carried out a discussion on chromosomes. We learnt about genetic disorders involving sex chromosomes.

Below are the list of disorders and a compilation of the information I gathered through internet research and through our class discussion:

1. Turner's Syndrome (XO)

- Receives no sex chromosome from the father, hence it has only one X sex chromosome from the mother

- Affects about 1 in every 2500 females

- Physical abnormalities: short stature, swelling, broad chest, low hairline, low-set ears, and webbed necks

- Ovaries do not develop or function properly (affect girl's sexual development and ability to have children)-->do not go through all the changes associated with puberty (e.g. menstrual cycle)-->infertile

2. Klinefelter's Syndrome (XXY)

- Exist in 1 out of every 650 males

- Have at least 2 X chromosomes and at least 1 Y chromosome

- Hypogonadism and reduced fertility

- Physical abnormalities: Feminine characteristics (larger breasts, less muscular body, less body and facial hair), often taller than other males

3. Super male (XYY)

- Male receives an extra Y chromosome so that he ends up with 47 chromosomes, instead of 46

- Affects 1 out of 1000 males

- Normal sexual development and normal fertility

- Increased risk of learning difficulties, delayed speech and language skills

A Super female is possible where there are 3 X chromosomes. However, as always X chromosomes will be suppressed (which in this case, is 2) so that only one can be expressed.

CSI Lesson 8 (17/8/11)

During today's Bio lesson, we carried out 3 blood tests on 6 samples to determine which was a blood sample. As Ms Tan revealed, the blood sample was from cockles and blood sample 6 was actually watermelon juice (no wonder it looked so familiar). The 3 blood tests were examples of blood tests forensic scientists would carry out on samples from crime scenes. However, more specific tests, such as a DNA test and Spectrophotometric test, could be carried out to determine if the blood is human blood.

Test 1 Results:

Samples tested +ve for catalase: 4, 5 and 6

Test 2 Results:
Samples that glow in the luminol test: 4 and 5

Test 3 results:

Observation: Only 4 turned an intense pink.

Conclusion of all 3 tests: Sample 4 contains blood and hence, is the real blood sample from the crime scene.

Questions

1. Why is it necessary to use more than one test to determine whether the given stain is blood?

It is because more than one chemical might react to the same test and yield positive results. Hence, more than one test is needed to eliminate uncertainties and other factors to achieve more conclusive results.

2. Once you know that a stain is real blood, what else would you do as a forensic scientist?

DNA analysis of the blood sample.

CSI Lesson 7: Understanding Heredity

My Biodata

A. Tongue-rolling-->No

B. Widow's Peak--> No

C. Cheek dimples-->I have it only on my right cheek so according to the worksheet, that should be considered a "no" :(

D. Earlobe Attachment--> No

E. Curly hair--> No

F. Cleft chin--> No

G. Mid-digital finger hair--> No

H. Right-handedness--> Yes

I. Freckles--> No

Individuality chart number: 15

After doing the questionnaire, 5 other people have the same individuality chart number as me.

Questions:

What is DNA?

It is deoxyribonucleic acid, which is the hereditary material of humans and other organisms. Information in DNA is stored as a code made up of 4 chemical bases: adenine (A), guanine (G, cytosine (C) and thymine (T).

What is a Gene?

Genes are a molecular unit of heredity that determines physical traits of organisms. They act as instructions to make molecules called proteins.

What is a Chromosome?

DNA molecules packaged into thread-like structures in the nucleus of the cell are called chromosomes. It is an organized structure of DNA and protein found in cells, containing genes, regulatory elements and nucleotide sequences.

What is Heredity?

It is the passing of physical or mental characteristics genetically from one generation to another

What is a Trait?

It is a distinguishing characteristic or genetically-determined characteristic.

Blood splatter graphs

Experiment 1

Experiment 2

Results of blood splatter experiments (6th CSI lesson cont'd)

Experiment 1

Table of results of vertical distance from which the blood droplet was dropped/cm VS. The diameter of the bloodstain/cm

Experiment 2

Table of results of angle of elevation of the surface/º VS. The length and width of the bloodstain/cm

Blood splatters

Projected bloodstains

When exposed blood source is subjected to force greater than the force of gravity.

Arterial spurt/gush

Resulting from blood exiting body under pressure from a breached artery

LARGE VOLUMES OF BLOOD (patterns created by same volume of blood,

from same source to target distance)

Projected blood (through syringe)
Spilled blood

Dripped Blood

What is shape of blood splatter?

It depends on a variety of factors, such as directionality. When a droplet of blood strikes a surface perpendicularly at 90 degrees, the resulting bloodstain will be circular. However, if it strikes the surface at an angle more or less than 90 degrees, the resulting bloodstain will be elongated or oval in shape.

Describe any other characteristic of the splatter.

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

Type of surface the splatter strikes, direction the blood splatter strikes the surface, angle of impact, the height the blood droplet is dropped from

Generate some hypotheses from the blood splatter patterns observed above.

The greater the height the blood droplet is dropped from, the larger the diameter of the resulting bloodstain. The greater the angle of inclination, the greater the length of the resulting bloodstain.

6th CSI Lesson

Partner: Crisann Moh (4)

Experiment 1

Resulting bloodstains (height of 10cm)
Experimental set-up
Resulting bloodstains (height of 60cm)
Resulting bloodstains (height of 100cm)
Resulting bloodstains (height of 150cm)

Height: Length 1st attempt)/ Length 2nd attempt)/ Length 3rd attempt (cm)

10cm: 0.8/0.8/0.8

30 cm: 1.1/1/1.2

60cm: 1.3/1.5/1.3

100cm: 1.8/1.8/1.9

150cm: 1.6/1.6/1.8

Experiment 2

Resulting bloodstains from the whole experiment

Angle(degrees): Length/ Width

1st 10: 1.5/1.4

2nd 10: 1.6/1.5

3rd 10: 1.7/1.6

1st 30: 1.8/1.2

2nd 30: 1.5/1.4

3rd 30: 1.9/1.2

1st 50: 1.8/1.1

2nd 50: 1.9/1.1

3rd 50: 1.8/1.1

1st 70: 3.7/0.8

2nd 70: 2.4/1.1

3rd 70: 4/0.8

Part 2

1st attempt

2nd attempt

Crisann and I favoured our 2nd attempt more as it was done more systematically.

From afar, the victim was shot in his leg, explaining the high-velocity blood splatter (in blue). With the shot, the murderer had probably intended to incapacitate the victim so that he could have his way with him. This revealed the cruel nature of the murderer as he wanted to make his victim suffer immeasurable pain before he died. When he was shot, the victim probably fell to his knees and the murderer took the opportunity to ram the back of his skull into the wall once, causing a flow pattern of blood (green at the top left-hand corner of the paper). Medium velocity impact splatters were also evident, indicating that he had probably been beaten. A fingernail probably caused the long contact bloodstain (swipe pattern that runs from the right of the image to the bottom). The thick transfer bloodstain that ran through the flow pattern of blood was probably caused by a blunt object.