Section 8 - Unit 21: Recombinant DNA technology Flashcards
State the purpose of restriction endonucleases (1 mark)
- Used to cut DNA
State the purpose of electrophoresis (1 mark)
- To separate pieces of DNA
State the name of the enzyme used to cut part of a plasmid (1 mark)
- Restriction endonuclease / enzyme
Describe what features of cut plasmids and lengths of foreign DNA allows their ends to join together (2 marks)
- Sticky ends / unpaired bases
- Which are complementary to each other
Explain how the strands of DNA are separated during the PCR (2 marks)
- Heating
- To break the hydrogen bonds
Explain why are primers required during PCR (1 mark)
- To allow DNA polymerase to attach
OR - Prevents strands from re-joining
Suggest why two different primers are required during PCR (1 mark)
- One primer used at beginning and one used at end
Describe how genetic fingerprinting may be carried out on a sample of panda DNA (6 marks)
- 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
Explain how genetic fingerprinting could allow scientists to identify the father of a child (2 marks)
- All bands in the child which don’t come from the mother
- Must be in the father’s fingerprint
Explain how electrophoresis separates fragments of DNA (2 marks)
- Move towards anode / because charged
- Different rates of movement related to charge / size
Describe what a DNA probe is (2 mark)
- Piece of DNA
- Single stranded
- Complementary to gene
Explain why radioactive DNA probes are used to locate specific DNA fragments (2 marks)
- DNA invisible on gel
- So radioactive allows detection
Describe how scientists could genetically engineer a type of bacteria to produce the enzyme which activates a drug (6 marks)
- 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
Explain one way in which PCR differs from DNA replication in a cell (2 marks)
- Uses heat
- To separate strands
Name the type of enzyme which can be used to produce DNA from mRNA (1 mark)
- Reverse transcriptase
Describe the role of the enzyme ligase (1 mark)
- Joins two pieces of DNA / sticky ends
A plasmid may be used as a vector. Explain what is meant by a vector. (2 marks)
- Carrier of DNA / gene
- Into cell / other organism / host
Molecular biologists often use plasmids which contain antibiotic resistance genes. Explain the reason for this (2 marks)
- Act as marker gene
- Allows detection of cells containing plasmid / DNA
Describe the polymerase chain reaction (6 marks)
- 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
Explain what is recombinant DNA (1 mark)
- Contains genes / sections of DNA from two species
What are DNA primers (1 mark)
- Short lengths of single stranded DNA
Describe how genetic fingerprinting is carried out (6 marks)
- 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
Use your knowledge of enzymes to explain why restriction enzymes only cut DNA at specific restriction sites (3 marks)
- 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
Describe how a gene could be removed from bacterial DNA (2 marks)
- Restriction enzyme
- Cuts DNA at specific point
