Undertanding DNA

Question 1

What does DNA stand for ?

Answer 1

Deoxyribo Nucleic Acid

Question 2

What does NCIDD stand for? And what is it?

Answer 2

National Criminal Investigation DNA Database.
Where DNA profiles are located. Where DNA profiles are compared to find a match.
If suspect known can compare directly

Question 3

How many areas of DNA are targeted to generate a profile?

Answer 3

21 areas

Question 4

Is DNA unique to every person?

Answer 4

Everyone expect identical twins

Question 5

What is DNA?

Answer 5

Building block for life. Another term for DNA is the genome. It is the genetic material found in the nucleus of all nucleated cells.

Question 6

What are the sources of DNA from most likely to least likely to get a profile?

Answer 6

Blood
Semen
Saliva
Hair
Trace DNA

Question 7

What are the factors affecting amount of cells deposited on a surface ?

Answer 7

TTPS
The contact time (longer time more cells)
Type of contact (vigorous?)
Type of person (shedder?)
Substrate (porous/ non porous)

Question 8

What is the Epithelium?

Answer 8

The primary body tissue in humans that lines the cavities and surface of structures and skin of the body.
Epithelium cells constantly shed from skin.
Approx 100 cells required to obtain DNA profile.

Question 9

What are the advantages of trace DNA?

Answer 9

Can get a DNA profile that may not have been gotten before. Good intel tool.

Question 10

What are the limitations of Trace DNA?

Answer 10

Invisible to human eye, so easy to miss.
Don’t know the source of the DNA and when and how it was deposited. Easily transferable.

Question 11

What is secondary transfer?

Answer 11

When two people come into contact there DNA can be put onto the next thing the other person touches.

Question 12

When can transfer of DNA occur?

Answer 12

Before the offence- innocent transfer
During the offence- what we are aiming to detect
After the offence- contamination

Question 13

What will depend on the retention of cells on a surface?

Answer 13

SEA
Type of surface
Type of environment
Type of activity the surface is subjected to (repeated handling)

Question 14

DNA collection reccomendations

Answer 14

Hard surface- swab with 70% ethanol
Porous surface- tape lift

Question 15

What is innocent transfer?

Answer 15

Legitimate contact prior to offence
- associates
- chance contact
- shared items
If the suspect has legitimate access to an area

Question 16

What is the likelihood ratio?

Answer 16

The chances that it could be the defendants DNA as it could be anyone else’s DNA that don’t have a profile on the system

Question 17

What is the aim of sampling for DNA?

Answer 17

To obtain a single source DNA profile

Question 18

Under what conditions should DNA be collected?

Answer 18

Relates to an indictable offence
Offender has not been ID
Item not suitable for fingerprint examination
DNA will be if significant value to investigations
Item has not been located on offender/ in vehicle they frequented
Item not visibly dirty or rusty
Item has not be exposed to weather for extended period
Item has been protected from contamination
Item has not be exposed to multiple people