8B- Gene Probes and Medical Diagnosis Flashcards
How can you look for alleles using DNA probes and hybridisation?
DNA probes can locate specific alleles of genes or see if a person’s DNA contains a mutated allele that causes a genetic disorder.
DNA probes are short strands of DNA. They have specific base sequence of a part of a target allele.
The probe will bind (hybridise) to the target allele if present within the DNA.
A DNA probe has a label attached, so it can be detected so it can be detected.
How is the location of specific alleles done?
A sample of DNA is digested into fragments using restriction enzymes and separated using electrophoresis.
The separated DNA fragments are then transferred to a nylon membrane and incubated with the fluroescently labelled DNA probe.
If the allele is present the DNA probe will bind.
The membrane is put under YV light and if the gene is present a band will show.
What is a DNA microarray?
A DNA microarray is a glass slide with microscopic spots of different DNA probes attached to it in rows.
A sample of flourescent DNA is washed over the array.
If it contains any DNA that match the probes, it’ll stick to the array.
It is then washed.
It is then put under UV light and the match will show up.
How do you produce a DNA probe?
You need to find the sequence of the allele that you want to screen for.
You then use PCR to produce multiple complementary copies of part of the allele.
What used does screening using DNA probes have?
It can help identify inherited conditions. People may choose to be screened as well as new born babies so treatment can begin ASAP.
Help determine how a patient will respond to specific drugs. Eg. The drug Herceptin can only be used on a Her2 proto-oncogene as it targets a specific receptor.
Help identify health risks. If a person knows they’re high risk they can make choices to reduce the risk. Eg Angelina Jolie.
However screening may lead to discrimination, eg companies may not hire high risk.
How can the results of screening be used for genetic counselling?
Genetic counselling is advising patients and their relatives about the risks of genetic disorders.
It involves advising people about screening if there’s a history and explaining the results.
If the results are positive the genetic counselling is used to advise the patient on the options of prevention or treatment available.
What are two examples of genetic counselling?
A woman with a family history of breast cancer may have genetic counselling to help decide whether or not to be screened. If it is positive for the BRAC1 they may choose to reduce the risk by having treatment, for example, a mastectomy.
Sickle cell anaemia is a recessive disorder in the haemoglobin gene. They may undergo genetic counselling to understand the risks of having children with the disease. Genetic counselling would provide an unbiased opinion on the possibility of having embryos screened.
How can gene probes be used in personalised medicine?
Your genes determine how your body responds to certain drugs. Different people respond to the same drug in different ways- which makes certain drugs more effective for some people than others.
Personalised medicines are medicines that are tailored to an individual’s DNA. If doctors have your genetic information, they can predict how you will respond to different drugs.
