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AQA A Level Biology > Section 8 - Unit 21: Recombinant DNA technology > Flashcards

Section 8 - Unit 21: Recombinant DNA technology Flashcards

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1
Q

State the purpose of restriction endonucleases (1 mark)

A
  • Used to cut DNA
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2
Q

State the purpose of electrophoresis (1 mark)

A
  • To separate pieces of DNA
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3
Q

State the name of the enzyme used to cut part of a plasmid (1 mark)

A
  • Restriction endonuclease / enzyme
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4
Q

Describe what features of cut plasmids and lengths of foreign DNA allows their ends to join together (2 marks)

A
  • Sticky ends / unpaired bases

- Which are complementary to each other

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5
Q

Explain how the strands of DNA are separated during the PCR (2 marks)

A
  • Heating

- To break the hydrogen bonds

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6
Q

Explain why are primers required during PCR (1 mark)

A
  • To allow DNA polymerase to attach
    OR
  • Prevents strands from re-joining
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7
Q

Suggest why two different primers are required during PCR (1 mark)

A
  • One primer used at beginning and one used at end
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8
Q

Describe how genetic fingerprinting may be carried out on a sample of panda DNA (6 marks)

A
  • DNA is cut
  • Using restriction enzyme
  • Use electrophoresis
  • To separate according to length
  • Transfer to nylon membrane
  • Make single-stranded
  • Apply probe
  • Radioactive / fluorescent
  • Reference to VNTRs
  • Autoradiography
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9
Q

Explain how genetic fingerprinting could allow scientists to identify the father of a child (2 marks)

A
  • All bands in the child which don’t come from the mother

- Must be in the father’s fingerprint

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10
Q

Explain how electrophoresis separates fragments of DNA (2 marks)

A
  • Move towards anode / because charged

- Different rates of movement related to charge / size

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11
Q

Describe what a DNA probe is (2 mark)

A
  • Piece of DNA
  • Single stranded
  • Complementary to gene
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12
Q

Explain why radioactive DNA probes are used to locate specific DNA fragments (2 marks)

A
  • DNA invisible on gel

- So radioactive allows detection

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13
Q

Describe how scientists could genetically engineer a type of bacteria to produce the enzyme which activates a drug (6 marks)

A
  • Cut gene out of cell / make gene using mRNA / obtain gene with restriction enzymes
  • Cut DNA using restriction enzyme / plasmid cut with restriction enzyme
  • Correct reference to sticky ends
  • Join DNA using ligase / insert gene into vector
  • Plasmid / named vector transferred to cell
  • Method of transfer e.g. heat shock
  • Reference to marker gene
  • Select bacteria containing new gene
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14
Q

Explain one way in which PCR differs from DNA replication in a cell (2 marks)

A
  • Uses heat

- To separate strands

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15
Q

Name the type of enzyme which can be used to produce DNA from mRNA (1 mark)

A
  • Reverse transcriptase
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16
Q

Describe the role of the enzyme ligase (1 mark)

A
  • Joins two pieces of DNA / sticky ends
17
Q

A plasmid may be used as a vector. Explain what is meant by a vector. (2 marks)

A
  • Carrier of DNA / gene

- Into cell / other organism / host

18
Q

Molecular biologists often use plasmids which contain antibiotic resistance genes. Explain the reason for this (2 marks)

A
  • Act as marker gene

- Allows detection of cells containing plasmid / DNA

19
Q

Describe the polymerase chain reaction (6 marks)

A
  • Heat DNA
  • Breaks hydrogen bonds / separates strands
  • Add primers
  • Add nucleotides
  • Cool
  • (to allow) binding of nucleotides / primers
  • DNA polymerase
  • Role of (DNA) polymerase
  • Repeat cycle many times
20
Q

Explain what is recombinant DNA (1 mark)

A
  • Contains genes / sections of DNA from two species
21
Q

What are DNA primers (1 mark)

A
  • Short lengths of single stranded DNA
22
Q

Describe how genetic fingerprinting is carried out (6 marks)

A
  • DNA extracted from sample
  • DNA cut / hydrolysed into segments using restriction endonucleases
  • DNA fragments separated using electrophoresis
  • Detail of process e.g. mixture put into wells on gel and electric current passed through
  • Immerse gel in alkaline solution / two strands of DNA separated
  • Cover with nylon / absorbent paper
  • DNA fixed to nylon
  • Radioactive marker / probe added
  • Areas with probe identified using X-ray film / autoradiography
23
Q

Use your knowledge of enzymes to explain why restriction enzymes only cut DNA at specific restriction sites (3 marks)

A
  • Different lengths of DNA have different base sequences / cut at specific sequence
  • Results in different shape of active site
  • Therefore (specific sequence) will only fit active site of enzyme
24
Q

Describe how a gene could be removed from bacterial DNA (2 marks)

A
  • Restriction enzyme

- Cuts DNA at specific point

25
Q

Explain how the use of a gene probe could enable the presence of a mutant allele of the cystic fibrosis gene to be detected (4 marks)

A
  • Probe will attach (to mutant allele)
  • Attaches to one DNA strand
  • As a result of complementary base pairing
  • Radioactivity detected on film / X-ray / by autoradiography
26
Q

What is meant by gene therapy (1 mark)

A
  • Introduction of a healthy gene / replacement of a defective gene
27
Q

Give two advantages of using a virus in gene therapy (2 marks)

A
  • Can enter cells
  • Replicates in cells
  • Targets specific cells
28
Q

Explain why the enzyme is called reverse transcriptase (2 marks)

A

Makes DNA from RNA

29
Q

Explain how you could use labelled DNA probes to show that the cells of a plant contain a specific gene (4 marks)

A
  • Extract DNA + add endonucleases
  • Separate fragments using electrophoresis
  • Treat to form single strands
  • The probe will bind to the gene
30
Q

Explain why a plant is able to use an insect gene to synthesise the insect protein within itself (3 marks)

A
  • Genetic code is universal
  • So the insect DNA can be transcribed
  • Can be translated
31
Q

Describe how bacteria can be genetically modified to produce human insulin (4 marks)

A
  • Cut out insulin gene / cut open plasmid with restriction enzyme
  • Use same restriction enzyme on second DNA
  • Reference to sticky ends
  • Use ligase to join 2 DNA molecules
  • Modified plasmid taken up by bacteria
32
Q

Explain how DNA can be broken down into smaller fragments (2 marks)

A
  • Restriction endonuclease/enzyme
  • Cuts DNA at specific base sequence
    OR
    (Breaks) phosphodiester bonds
    OR
    (Cuts DNA) at recognition/restriction site

AQA A Level Biology (14 decks)

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