Genetic Screening & Counselling Flashcards
What are DNA probes?
short, single-stranded pieces of DNA that are labelled radioactively or fluorescently so that they can be identified
What are DNA probes used for?
They are used to locate specific alleles of genes
What does the use of DNA probes allow us to do?
To screen patients for heritable conditions, drug responses or health risks
How are DNA created, what particular feature do they have?
DNA probes are created to have a complementary base sequence to the allele that is being screened for
How do they go about mixing the DNA probe with the patient’s DNA?
The patient’s DNA sample is treated to make it single-stranded and then it is mixed with the DNA probes
What does hybridisation mean?
It is when the DNA probe will ‘hybridise’ if the patient has that particular allele - the label indicates its presence.
Define the term hybridise:
join together, in this case, the DNA probe and the patient’s single stranded DNA
Name the two processes that make up DNA hybridisation:
Denaturation and Annealing
Describe the process denaturation during DNA hybridisation:
The patient’s DNA sample is heated to make it single-stranded
The heat causes the hydrogen bonds between bases to break
Describe the process of annealing during DNA hybridisation:
The patient’s single stranded DNA sample is mixed with the DNA probe and cooled so that any complementary sequences that have aligned, can form hydrogen bonds between the bases.
What else could anneal apart from the DNA probe to the patient’s DNA?
Some of the patient’s DNA samples will anneal back together, but some will anneal with the DNA probe
Give an example of a DNA sequencing technique:
The Sanger method
In order to locate a specific allele, what must be known?
The DNA base sequence must be known to then create the DNA probe
How can we find out the DNA base sequence of the specific allele in order to create the DNA probe?
It can be determined using DNA sequencing techniques
How can we produce a DNA fragment for the DNA probe?
gene machine
How do we amplify the DNA fragment in order to make multiple DNA probes?
Using the polymerase chain reaction (PCR)
What happens to the DNA probe after it has been amplified using PCR?
The label is then added
What are the two possible labels that you can add to the DNA probe?
A radioactive nucleotide which contains the isotope (32)P
OR
A fluorescent label which emits light under UV light
What is the next step after DNA hybridisation?
The DNA is washed so that any unbound DNA probes are washed away
What indicates whether the allele of interest is present in the patient’s DNA?
The presence of the radioactive or the fluoresence label
Describe what happens during genetic screening and what apparatus is used?
A microarray is used which has multiple DNA probes on it all with complementary sequences to a range of specific alleles.
What can genetic screening be used for?
This method can be used to screen for potential genetic disorders or for ‘cancer-causing oncogenes’
How is a micro-array more efficient?
It can be used to screen for multiple diseases simultaneously where multiple different DNA probes are attached
Why might someone want to have their DNA screened?
Personalised medicine, so the drug that you take can be tailored for your paticular genotype
What are the advantages of genetic screening enabling personalied medicine?
Certain drugs, painkiller, can become more/less effective depending on your genotype.
It can help determine the best dose, which increases the effectiveness, safety + saves money
Give an example representing why having your DNA screened is important:
Some diabetics with a particular genotype can take vit.E to reduce their chances of developing cardiovascular disease whereas for other diabetics with a different genotype, it will increase their chances.
What is genetic counselling?
It is like a type of social work, where people can have their family history researched to consider the likelihood of them carrying any alleles linked to diseases before starting a family, or for their general health.
During genetic counselling, what are patients informed of?
Any potential risks to themselves or to their future offspring if they were to carry the allele.
What are some disorders that people can screen for?
Sickle-cell anaemia, cystic fibrosis, and if there is a family history of breast cancer: you could then opt for a masectomy or regular screening for tumours and reduce environmental risk factors.
