3.8.4.2 and 3 DNA fingerprinting and Genetic counselling (Unit 8 Gene Tech) Flashcards
What are the two methods that can be used in gene therapy?
germ line therapy and somatic cell therapy
How does germ line gene therapy work?
Replacing or supplementing the defective gene in the fertilised egg. This means all of the developing cells will be normal, as will the cells of the next generation. The solution is permanently but currently prohibited for ethical reasons
How does somatic cell gene therapy work?
Targets the affected tissues (such as the lungs). This does not pass to the next generation as it is not in the gametes. The treatment is also short lived for the patient as the lung cells are continually dying and being replaced. The treatment therefore needs to be repeated every few days in some cases.
Which two vectors can be used to get a healthy gene into somatic cell of a patient?
- Using a harmless virus
- Wrapping the gene in lipid molecules
Why might gene therapy be unsuccessful?
- Adenoviruses may cause infection.
- Patients may develop immunity to the adenoviruses.
- The liposome aerosol may not be fine enough to pass through the bronchioles in the lungs.
- The CFTR gene may not be expressed even when successfully delivered to the epithelial cells.
What is a DNA probe?
The DNA probe is a short, single stranded section of DNA that has an identifiable label attached to it.
What are the two types of DNA probes and how do they work?
- Radioactively labelled probes – made of nucleotides with the isotope 32P. A photographic plate exposed to -adioactivity is used to identify the probe.
- Fluorescently labelled probes – emit light under certain conditions.
How do DNA probes result in a scientist being able to identify a mutant allele in a patient?
A probe with bases complementary to the bases on the portion of the gene we want to find is made.
The DNA being tested is treated to separate the strands.
The separated strands are mixed with the probe which binds the complementary bases on the strands. This is DNA HYBRIDISATION.
The site at which the probe binds can be identified by radiation or fluorescence emitted.
What is the point of genetic screening?
Genetic screening is carried out on individuals who may carry the mutant gene, this is determined by looking at their family history.
Screening can allow a couple to find out the chances of having a child with a genetic disorder. Couple as risk can then be referred to a genetic Councillor for advice.
If a positive gene test result reveals that a seemingly healthy individual carries or has a genetic mutation associated with a specific disorder, what would a ‘negative gene test result’ be? How about a ‘false negative gene test result’?
A negative gene test result reveals that the faulty gene being looked for is not there. A false negative result means that further testing is probably needed as there was a problem with the procedure.
Why are introns (not exons) used in genetic fingerprinting?
Genetic fingerprinting is based on the fact that DNA the genome of any organism has many repetitive non-coding bases – INTRONS (e.g. 95% of human DNA does not code for any characteristic).
Introns contain repetitive sequences of DNA called core sequences which differ in everyone (except identical twins).
What are the stages of DNA fingerprinting?
Extraction, Digestion, Separation, Hybridisation, Development
In DNA fingerprinting what happens in Extraction?
extract DNA from the sample (however small) by separating it from the rest of the cell. PCR can be used to make more if necessary
In DNA fingerprinting what happens in Digestion?
the DNA is cut into fragments using restriction endonucleases (chosen as they cut close to but not inside core sequences).
In DNA fingerprinting what happens in Separation?
gel electrophoresis separates the DNA fragments according to size. The gel is then immersed in an alkali to separate the 2 DNA strands. The single strands are then transferred onto a nylon membrane by a technique called southern blotting
