The control of gene expression (AQA A2 Biology) PART 8 of 8 TOPICS
Gene technologies allow the study and alteration of gene function allowing a better understanding of organism function and the new design of industrial and medical processes – genetic fingerprinting:
Genetic fingerprint is a banding pattern produced by DNA that is particularly unique to that individual. This is useful at a crime scene or the establishment of paternity. This is how it’s done:
- Collection: The sample of DNA is collected which can come from the cheek cells, hair, semen, blood e.t.c.
- Extraction: The DNA fragment of variable number tandem repeats (bases that are repeated in the introns sections of the DNA) is obtained. NB: The process of extraction does not need to be known for the exam. Variable number tandem repeats can be abbreviated into VNTRs. In some text books and online resources the word ‘minisatellites’ may be used. This is an old name for variable number tandem repeats which is not used now.
- Digestion: Restriction enzymes cut the DNA close to but not in the VNTR regions allowing the DNA fragments to keep the lengths for the characteristics to show up unique to that individual.
- Separation 1: Gel electrophoresis takes place and then the DNA double strands are broken by breaking the hydrogen bonds using alkaline solution or DNA helicase.
- Separation 2: The DNA is then transferred onto a nylon membrane using a weight. NB: The name of this process, Southern transfer does not need to be known for the AQA exam.
- Hybridization: Labelled DNA probes with markers on complementary to the desired gene are added to the DNA and then is washed to remove any of unbound DNA probes. Then the membrane is dried.
- Development: An x-ray film is placed over the membrane to make the bands visible which are known as DNA fingerprints.
] That’s all that you need to know 🙂 [