Forensic Biology

Question 1

What do Forensic Biologist analyze?

Answer 1

Hair and fibre, body fluids ID, DNA analysis

Question 2

What do Forensic Chemists analyze?

Answer 2

Trace evidence, paint, GSR, glass, fire, explosives, unknown chemical, hair and fibre

Question 3

What do Forensic Toxicologists analyze?

Answer 3

Impaired driving, suspected poisoning, suspicious deaths

Question 4

What type of items so Forensic Biologists deal with?

Answer 4

Clothes, swabs, weapons, vehicles, human remains, and discard samples

Question 5

What is the process of analyzing evidence?

Answer 5

1. Evidence recovered from scene
2. Submitted by police
3. Processed by CRO at CFS
4. Evidence sealed and bar-coded
5. Case assessed by scientist
6. Screen item for body fluid

Question 6

What does the Screening Unit do?

Answer 6

• Examine item for body fluid
• Process/sample items for DNA
• Process bone samples
• Process comparison samples

Question 7

How are the items examined?

Answer 7

• Visual
• Alternative light sources
• Microscope

Question 8

How can you detect blood?

Answer 8

-Kastle-Meyer test 
o Methanol
o Phenolphthalein
o Hydrogen peroxide
-Positive means human

Question 9

How do you detect saliva?

Answer 9

➢ Phadabas press test

o Put on paper, wait and turn blue

Question 10

How do you detect semen?

Answer 10

-Presumptive chemical detection of acid-phosphatase- brentamine fast blue
-Microscopic exam of sperm
-After ejaculation,
• Oral- up to 1 day
• Rectal- up to 3 days
• Vaginal- up to 7 days
o Majority of semen lost from vagina within 2-3 days
•A comparison sample from the last previous consensual partner may be obtained for exclusion

Question 11

How much DNA is in 1 drop of semen, 1 drop of saliva, and 1 drop of blood?

Answer 11

• 1 drop saliva- 150ng of DNA
• 1 drop blood- 900ng of DNA
• 1 drop semen- 1500ng of DNA

Question 12

What is Short Tandem Repeats?

Answer 12

At numerous areas in out DNA there are repeated regions, STRs that can be variable between individuals. When we look at several of these repeated regions, we can build a DNA profile.

Question 13

How do you isolate DNA?

Answer 13

• Solubilisation of the strain components, denaturation and hydrolysis of proteins, removal of denatured proteins, purification of DNA
• AKA, break open the cell membrane, freeing the DNA from the cell and removing proteins and other inhibitors.

Question 14

How do you quantify DNA?

Answer 14

Utilize probes tagged with fluorescent molecules to determine how much DNA is present

Question 15

How do you amplify DNA?

Answer 15

• Polymerase chain reaction (PCR)

- Cycles of heating and cooling, exponential copies, until you get a very large number of copies.

Question 16

When a person cannot be excluded as the contributor of a DNA profile, what are two things it means?

Answer 16

• The person is the contributor

- Or the person is not the contributor and a coincidental match has occurred

Question 17

What cab Y-STRs assist in?

Answer 17

• Can assist in providing a DNA profile where the quantity of female DNA far exceeds the quantity of male DNA
• Can assist in determining the total number of males contributing to a mixture of DNA
• Familial DNA studies-paternity, elimination of complete segment of familial

Question 18

What is CODIS?

Answer 18

• Combined DNA Index System

- Software program used for housing and comparing DNA profiles