21.5 Genetic fingerprinting Flashcards
What does the process of genetic fingerprinting rely on
That the genome of most eukaryotic organisms contains mainly repetitive, non-coding bases of DNA
These are called variable number tandem repeats (VNTRs) for every individual the number and length of VNTRs has a unique pattern
How does gel electrophoresis work
DNA fragments are placed on to an agar gel and a voltage is applied across it. The resistance of the gel means that the larger the fragments, the slower they move. Therefore, over a fixed period, the smaller fragments move further than larger ones.
What must happen to larger genes and whole genomes before gel electrophoresis
Must be cut into smaller fragments by restriction endonucleases
What are the 5 stages of genetic fingerprinting
- Extraction
- Digestion
- Separation
- Hybridisation
- Development
What is the process of extraction (1)
Phenol and chloroform is used to separate DNA from the rest of the cell. If the DNA quantity is small it can be increased by using the polymerase chain reaction
What is the process of digestion (2)
The DNA is cut into fragments, using the same restriction endonucleases. RE’s are used because they cut close to, but not within, the target DNA
What is the process of separation (3)
Fragments are separated using gel electrophoresis and then immersed in alkali to separate the double strands to single strands. The DNA fragments are then transferred from the gel to nylon membrane
What is the process of hybridisation (4)
DNA probes are added to label the fragments. These radioactive probes attach to specific fragments
What is the process of development (5)
Membrane with radioactively labelled DNA fragments is placed onto an X-ray film. Development of the X-ray film reveals dark bands where the radioactive DNA probes have attached
What are the 4 uses of genetic fingerprinting
- Determining genetic relationships
- Forensic science
- Medical diagnosis
- Plant and animal breeding
