3.8.4.2 Differences in DNA

Question 1

What is a DNA probe?

Answer 1

short, single-stranded length of DNA with a label attached to make it identifiable

Question 2

Give 2 examples of DNA probes

Answer 2

1. Radioactively labelled probes (made of isotope phosphorus-32, identified using an X-ray film exposed to radioactivity)
2. Fluorescently labelled probes (emit light when bound to target DNA sequence)

Question 3

Probe has base sequences that are…

Answer 3

complementary to the part of the sequence of DNA of allele we want to find

Question 4

What is DNA hybridisation?

Answer 4

-section of DNA/ RNA is combined with single-stranded section DNA
-DNA strands are separated by heating (denaturation)
-cooled, comp bases anneal to strand

Question 5

How do you identify a mutant allele?

Answer 5

1. Determine sequence of nucleotide bases of mutant allele (using DNA sequencing techniques)
2. Produce fragment of DNA with sequence of complementary bases to mutant allele
3. DNA probe is made by attaching fluorescent marker to DNA fragment
4. Multiple copies of DNA probe are produced (PCR)
5. DNA from person we are analysing is heated (to separate double strands)
6. Separated DNA strands are cooled in mixture with many DNA probes
7. If mutant allele is present, probe will bind to it
8. DNA is washed clean of any unattached probes
9. Remaining hybridised DNA will now be labelled (fluorescently)

Question 6

What is personalised medicine?

Answer 6

using a person’s alleles to choose the most effective drug and dose; avoiding harmful side effects
(e.g. how they metabolise a drug)

Question 7

What is genetic counselling (examples)?

Answer 7

-explaining test results
-risks of being affected or being a carrier of a disease
-options for having children, screening and treatment