Gene Technology- 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

What are DNA probes?

Answer 2

Short strands of DNA that have a specific base sequence that’s complementary to the base sequence of a part of a target allele you’re looking for

Question 3

What is attached to a DNA probe?

Answer 3

A label that is either radioactive, or fluorescent

Question 4

How is a DNA probe used?

Answer 4

1. A sample of DNA is digested into fragments using restriction enzymes and separated using electrophoresis
2. Separated DNA fragments are transferred to a nylon membrane and incubated with the fluorescently labelled DNA probe
3. If the allele is present, the DNA probe will hybridise (bind) to it
4. The membrane is exposed to UV light and there will be a fluorescent band if the gene is present

Question 5

What is a DNA microarray?

Answer 5

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

Question 6

Why is a DNA microarray used?

Answer 6

It can screen lots of genes at the same time

Question 7

How is a DNA microarray used?

Answer 7

1. A sample of fluorescently labelled DNA is washed over the array
2. If the labelled DNA contains any DNA sequences that match any of the probes, it will stick to the array
3. The array is washed to remove any DNA that hasn’t stuck to it
4. Array is visualised under UV light so that any labelled DNA attached to a probe will fluoresce
5. Any spot that fluoresces means that the DNA contains that specific allele

Question 8

What do you need to produce a DNA probe?

Answer 8

To first sequence the allele that you want to screen for, then use PCR to produce multiple complementary copies of part of the allele

Question 9

What can screening using DNA probes be used for?

Answer 9

• Help identify inherited conditions
• Help determine how a patient will respond to specific drugs
• Help identify health risks

Question 10

What is genetic counselling?

Answer 10

Advising patients and their relatives about the risks of genetic disorders

Question 11

What does genetic counselling involve?

Answer 11

Advising people about screening and explaining the results of a screening

Question 12

How is genetic counselling used when screening is positive?

Answer 12

To advise the patient on the options of prevention or the treatment available

Question 13

What are personalised medicines?

Answer 13

Medicines that are tailored to an individual’s DNA