21.5 Genetic fingerprinting

Question 1

genetic fingerprinting

Answer 1

• relies on the fact that the genome of most eukaryotic organisms contain many repetitive non coding bases of DNA

Question 2

Variable number tandem repeats (VNTRs)

Answer 2

• DNA bases that are non coding
• different in all individuals except identical twins
• the more closely related two individuals are the more similar the VNTRs will be

Question 3

Gel electrophoresis

Answer 3

• used to separate DNA fragments according to their size
• DNA fragments are placed on to an agar gel and a voltage is applied across it
• the resistance of the gel means the larger the fragments the more slowly than move
• over a fixed period the smaller fragments move further than the longer ones
• if DNA fragments are labelled with radioactive DNA probes their final position in the gel can be determined by placing a sheet of X ray film over the agar gel
• radioactivity from each DNA fragment exposes the film and shows where the fragment is situated on the gel

Question 4

what are the 5 main stages of making a genetic fingerprint

Answer 4

1. extraction
   - extract the DNA by separating it from the rest of the cell
   - PRC can be used to increase quantity
2. digestion
   - DNA cut into fragments using restriction endonucleases
3. separation
   - fragments of DNA separated according to size by gel electrophoresis
   - gel is then immersed in alkali to separate the double strands into single strands
4. hybridisation
   - radioactive or florescent DNA probes are used to bind with VNTRs
5. development
   - X - ray film is put over the nylon membrane and exposed by the radiation form the radioactive probes
   - because these points corresponded to the position of the DNA fragments a series of bards is revealed
   - The pattern of the bands is unique to everyone but identical twins

Question 5

uses of DNA fingerprinting

Answer 5

1. genetic relationship and variability
2. forensic science
3. medical diagnosis
4. plant and animal breeding