3.4.8 Gene probes Flashcards

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1
Q

What are gene probes?

A
  • short lengths of single stranded DNA with a complementary base sequence to target allele
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2
Q

What are gene probes used for?

A

Used to locate / identify specific alleles of genes

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3
Q

Uses of DNA screening (4)

A
  • Identifying inherited conditions e.g. Huntington’s
  • Identifying health risks e.g. risk of developing cancers
  • Identifying whether drugs will be effective
  • Personalised medicined tailored to individual’s DNA
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4
Q

What does a genetic counsellor do? (3)

A
  • Advising patients and relatives about risks of genetic disorders
  • Advising about and explaining results of screening
  • Gives options of prevention or treatment
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5
Q

How and why are DNA probes detected?

A
  • Able to see if probe has attached to gene - makes fragment visible
    1. Fluorescent labels - detected by UV light
    2. Radioactive labels - detected using x-ray film
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6
Q

How does gel electrophoresis separate DNA fragments? (2)

A
  1. Separates fragments of DNA using electricity
    - the DNA is slightly negatively charged so is repelled from the negative electrode and attracted toward the positive electrode
  2. Fragments separated by size due to the the gel
    - gel provides resistance meaning smaller molecules mover further and faster than heavier ones
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7
Q

4 stages of using gene probes

A
  1. Extraction
  2. Create probes
  3. Split DNA
  4. Add probe
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8
Q
  1. Extraction
A
  • extract DNA from patient cells
  • amplify the DNA using PCR
  • cut the DNA using restriction endonuclease and separate fragments by gel electrophoresis
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9
Q
  1. Create probes
A
  • specific complementary gene probes for the target allele created with a gene machine
  • these are amplified using PCR
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10
Q
  1. Split DNA
A
  • patient DNA is split into 2 strands - H bonds between bases broken by heating to 95 c
  • this exposes bases for the DNA fragments to attach to
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11
Q
  1. Add probe
A
  • gene probe added to patient DNA

- if the allele is present the probe will bind to one strand of the DNA - DNA hybridisation

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12
Q

What is DNA hybridisation?

A

2 complementary single stranded DNA molecules combine through base pairing to form a double stranded DNA molecule

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13
Q

Why are DNA fragments transferred?

A
  • DNA fragments transferred to a nylon membrane so DNA doesn’t degrade
  • then heated to cause DNA strands to separate, incubated at 55 c with a DNA probe allowing probe to bind to target allele
  • washed to remove unbound probe
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