DNA profiling

Question 1

Is everyone’s DNA the same?

Answer 1

No, except for identical twins

Question 2

What is DNA profiling used for?

Answer 2

Using DNA to distinguish between and/or identify individuals

Question 3

Who developed DNA fingerprinting and when?

Answer 3

Professor Alec Jeffreys in 1984

Question 4

Why is DNA profiling so good?

Answer 4

The chances of two people having exactly the same DNA profile is 30,000 million to 1 (except for identical twins)
DNA is robust and stable under most environmental conditions
DNA can be isolated from a wide range of biological samples likely present at a crime scene

Question 5

Advantages of DNA fingerprinting?

Answer 5

1. The source of DNA doesn’t matter – it is the same in all sources (blood, semen, sputum, skin etc)
2. Even with very small samples (a blood spot, single hair follicle, lip-prints on a glass, physical fingerprints, saliva/skin on a cigarette butt etc)
3. Methods are fast and relatively cheap
4. Data are complied in databases, and are easily searched

Question 6

What cells can be used for DNA fingerprinting?

Answer 6

1. Blood (White blood cells)
2. Semen (Sperm cells)
3. Hair with roots (Hair follicle cells)
4. Skin, dandruff (Skin cells)
5. Sweat stains (Skin cells sloughed off)
6. Vaginal fluids (Mucosal surfaces)
7. Nasal secretions (Mucosal surfaces)
8. Urine (Mucosal surfaces)
9. Faeces (Digestive system cells)

Question 7

What are the uses of DNA fingerprinting?

Answer 7

Identification of remains
Murder/rape cases
Paternity cases
Exoneration!

Question 8

Does every cell in your body contain the same set of DNA?

Answer 8

Yes

Question 9

What percentage of our DNA do we share with everyone else?

Answer 9

99.9%

Question 10

The remaining 0.1% of our 3 billion nucleotides that we don’t share with others, is this a significant and detectable level of difference?

Answer 10

Yes, this is 1 out of every 1000 nucleotides

Question 11

Where do most of the DNA variations take place?

Answer 11

Non-coding junk DNA

Question 12

What happens when mutations occur within the non-coding DNA in an organism?

Answer 12

Nothing, the organism can tolerate and accumulate these mutations with no affect to the organism.

Question 13

What does RFLPs stand for?

Answer 13

Restriction Fragment Length Polymorphisms

Question 14

What are STRs?

Answer 14

Short Tandem Repeats

Question 15

Is this an example of an STR?

ACTG-GCC-GCC-GCC-GCC-ATCGACC

Answer 15

Yes this is a 4 tandem repeat

Question 16

What does SNP mean?

Answer 16

Single nucleotide polymorphism

Question 17

What percentage of DNA is tandemly repetitive?

Answer 17

10-15%

Question 18

What are STRs also known as?

Answer 18

Satellite DNA

Question 19

Variations in satellite length are used for DNA fingerprinting, but what is the most useful type?

Answer 19

Microsatellite DNA

Only a few base pairs that are repeated 10-100 times

Question 20

On a gel there are two bands, where are they likely to have come from?

Answer 20

One from each parent