Dna

CSI lesson 15/8/11

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. 

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

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

Blood splatter data(height and diameter of splatter relationship)

Blood splatter data(angle of elevation)

Chromatography data

Blood splatter!

Blood splatter 1: The shape of the blood splatter is one large drop of blood with small drops surrounding it. This is probably created by drops of blood dropping onto a same spot. This means that the surrounding drops of blood are the result of blood dropping onto other drops of blood already on the surface and thus the impact resulting in small drops of blood being scattered around.


Blood splatter 2: This blood splatter consists of 2 main areas which contain larger amounts of blood and small droplets of blood surrounding them. As the drops of blood are not complete, they look like they may have been smudged, such as by another object coming into contact with the splatter. May have been created through a gunshot?


Blood splatter 3: The shape of the blood splatter is long and slants slightly upwards from left to right, and is more narrow on the left side than the right side. This means that the direction of the blood was north east. This splatter is most likely created by blood being flung off a swinging item that was bloody.


Blood splatter 4: The blood splatter covers a large area and consists of many smaller oval shaped splatters which have drops of blood dripping downwards. The splatter looks like it was created intentionally due to the relatively regular pattern of the blood splatter. It could have been created using a product such as red paint.

What is the shape of the blood splatters?

Circles and ovals, of varying lengths and widths.

Describe any other characteristics of the splatter.

- Jagged edges

- 2 distinct areas(inner and outer) the inner portion being a darker colour than the outer portion

- blood dropped vertically creates a blood splatter in the shape of a circle while blood dropped an an angle creates one that is in the shape of an oval, with increase in angle causing increase in the length and decrease in diameter of the blood splatter.

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

- angle at which the blood drop reaches the place of contact

-  the distance blood is dropped at from the point of contact 

- the surface of point of contact 

- amount of blood that is dropped 

- force used to create blood splatter(high impact/low impact)

- viscosity of blood used

Generate some hypotheses from the blood splatter patterns observed above.

1) The greater the height from which the blood is dropped, the larger the size of the blood splatter

2) The greater the angle of the plane used, the greater the length of the blood drop and the smaller the width of the blood drop

3) When a droplet of blood strikes a horizontal surface at 90 degrees it produces a circular stain. While droplets of blood that strike the surface at an angle produce a oval shaped stain

2. If dropped from the same height from the plane, the length of the blood drops will increase and the width of the blood drops will decrease as the angle of the plane on which the blood is dropped increases.

Fingerprinting

1. Wood Glue method

- Where are the pores found? Are they regularly spaced?

Pores are found throughout the surface of our skin, and are regularly spaced all over the epidermis of our skin.

- Are the lines of your print equally spaced throughout?

Yes

2. Cyanoacrylate (superglue) Fuming method

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

You can use more superglue to fume the print for a longer period of time or oil your fingers before creating fingerprints on the plastic sheet used so that the print is more obvious and visible

3. Iodine Fuming method

- What are the possible substances that may be used to render the prints more permanent?

The paper used as the base can affect how long the prints last for

- Why does the print disappear?

The prints appear on the paper because the iodine sublimes. However this process is reversible and thus 

4. Powder Dusting method

Questions for the lesson:

- What is magnetic powder dusting and how does it work?

magnetic powder is used on nonmagnetic surfaces. With magnetic powder, there is no brush with fibers to touch and possibly damage the print. The powder is not itself magnetic, but is attracted by a magnet and carried as whiskers by a magnetic wand. Nothing but the powder itself touches the print. The wand is a closed, hollow tube containing a magnet on a rod. When the rod is pushed in, the magnet is located I the end of the tube and the powder clings to that end. When the rod is pulled out, the magnet is moved to the center of the tube and the powder falls off. With the rod in and a cluster of powder whiskers on the end, you are ready to dust for latent prints.

Creating my own fingerprint!

Questions for this activity:

- Compare the fingerprint patterns on your right and left hand. Are they mirror images of each other?

- What kind of patterns do you see?

whorl

- Do the loops curve in the same or in different directions in different fingers?

they curve in different directions

- Compare the size of the patterns e.g. how many ridges make up a loop?