Genetic Counselling and Personalised Medicine
Laura Armstrong & Joe Wolfensohn
Teachers
Recall Questions
This topic requires prior knowledge of DNA probes and genetic screening. You can test your knowledge on these below.
What is a DNA probe?
A short, single-stranded DNA sequence that is complementary to a target gene and is labelled for detection.
How is a DNA probe used in genetic screening?
It binds to complementary DNA if the target gene/mutation is present, allowing detection.
What is the purpose of genetic screening?
To identify individuals carrying alleles associated with genetic conditions or increased disease risk.
Topic Explainer Video
What is Genetic Counselling?
Genetic counselling is the process where individuals or families receive advice and information about:
- Genetic conditions they might carry or be at risk of.
- The likelihood of passing on genetic disorders to offspring.
- The implications of genetic test results for their health, reproduction, and lifestyle.
Key focus: Helping people make informed decisions based on genetic information.
Examples of Genetic Counselling in Practice
|
Condition |
Role of Genetic Counselling |
|---|---|
|
Cystic Fibrosis (CF) |
Advising couples who are carriers of the CFTR gene mutation about the risk of having an affected child. |
|
BRCA1/BRCA2 Mutations |
Helping individuals understand their increased risk of breast and ovarian cancer and explore preventive options. |
|
Huntington’s Disease |
Providing support and information to individuals at risk of inheriting the faulty Huntington gene. |
What is Personalised Medicine?
Personalised medicine uses information about an individual's genome to:
- Predict their response to certain treatments.
- Choose the best drug and correct dose for maximum effectiveness with minimal side effects.
It recognises that genetic differences mean people can respond differently to the same medication.
Examples of Personalised Medicine in Practice
|
Disease/Treatment |
How Personalised Medicine Helps |
|---|---|
|
Breast cancer (HER2 gene mutation) |
Only patients whose cancer cells have a specific mutation are given herceptin because this drug targets a specific receptor only found on cells with this specific mutation. |
|
Cystic Fibrosis (specific mutations) |
Some drugs (e.g., ivacaftor) are prescribed only if a patient's specific CFTR mutation will respond. |
|
Warfarin dosing |
Genetic tests can determine the correct starting dose of warfarin (a blood thinner), avoiding dangerous over- or under-dosing. |
Key Terms
- Genetic Counselling: Advising individuals/families on risks and implications of genetic. conditions
- Personalised Medicine: Tailoring medical treatments based on an individual's genetic. information
- DNA Screening: Testing DNA to detect alleles linked to genetic diseases.
- Carrier: An individual who carries one copy of a mutated gene but does not usually show symptoms.
No answer provided.
Practice Question
Use the exam tips to answer the practice question from the TikTok on your own, then watch the video to see how well you did!
Exam Tips
When answering questions:
Knowledge of specific examples are not required - you will use the information provided in an exam question and your own knowledge to formulate an answer.
No answer provided.
Exam-Style Question & Model Answer
Huntington’s disease is a genetic condition that damages the brain and nervous system. The gene involved contains a section of DNA with many repeats of the base sequence CAG. The number of these repeats determines whether or not an allele of this gene will cause Huntington’s disease.
• An allele with 40 or more CAG repeats will cause Huntington’s disease.
• An allele with 36 – 39 CAG repeats may cause Huntington’s disease.
• An allele with fewer than 36 CAG repeats will not cause Huntington’s disease.
The graph shows the age at which a sample of patients with Huntington’s disease first developed symptoms and the number of CAG repeats in the allele causing Huntington’s disease.
People can be tested to see whether they have an allele for this gene with more than 36 CAG repeats. Scientists suggest that the results can be used to predict the age at which someone will develop Huntington’s disease. Use information from the graph to evaluate this suggestion (3)
Negative correlation, Accept a description for ‘negative correlation’
Wide range / variation of results (e.g. people with the same number of CAG repeats have wide variation in the age they develop symptoms)
Overlap between results (e.g. people with different numbers of CAG repeats can develop symptoms at the same/ similar age)
Correlation does not prove causation, other factors may be involved (in age of onset)
Practice Question
Try to answer the practice question from the TikTok on your own, then watch the video to see how well you did!