CGE: Gene Probes and Medical Diagnosis

Question 1

What can DNA probes be used for?

Answer 1

To locate specific alleles of genes or to see if a person’s DNA contains a mutated allele that causes a genetic disorder.

Question 2

DNA probes

Answer 2

Short strands of DNA, which have a specific base sequence that is complementary to the base sequence of part of the target allele.

Question 3

Describe how a single DNA probe can be used to identify the presence of a gene:

Answer 3

• Sample of DNA is digested into fragments using restriction enzymes and separated using electrophoresis.
• Separated DNA fragments are transferred to a nylon membrane and incubated with fluorescently labelled DNA probe.
• If allele is present, DNA probe will hybridise to it.
• Membrane is then exposed to UV ligth and if gene is present there will be a fluorescent band.

Question 4

Describe how a DNA probe can be used as part of a DNA microarray:

Answer 4

• Fluorescently labelled human DNA is washed over array.
• If DNA contains any sequences that match any probes, it will hybridise.
• Array is washed to remove DNA that hasn’t hybridised.
• Array is visualised under UV light - any labelled DNA attached to a probe will fluoresce.
• Fluorescing spot means DNA contains specific allele.

Question 5

DNA microarray

Answer 5

A glass slide with microscopic spots of different DNA probes attached to it in rows.

Used to screen lots of genes at the same time.

Question 6

How do you produce a DNA probe?

Answer 6

• Sequence the allele that you want to screen.
• Use PCR to produce multiple complementary copies of part of allele.
• These are the probes.

Question 7

Give 3 uses of DNA probes:

Answer 7

1. Identify inherited conditions.
2. Determine how a patient will respond to specific drugs.
3. Identify health risks.

Question 8

What is often done after genetic screening?

Answer 8

Genetic counselling

Question 9

Genetic counselling is advising patients and their relatives about the risks of genetic disorders.

Question 10

What are the 3 main things that genetic counselling does?

Answer 10

• Advises people about the screening
• Explains results of screening
• Advises on options of prevention or treatment available

Question 11

What two areas can the results of screenings be used in?

Answer 11

Genetic counselling

Personalised medicine

Question 12

Personalised medicines

Answer 12

Medicines that are tailored to an individual’s DNA.

Question 13

What is the point of personalised medicines?

Answer 13

Allows a doctor to predict how you will respond to different drugs, based on your genes, and only prescribe the ones that will be most effective for you.