Gene Technology Flashcards
Describe and explain how the polymerase chain reaction (PCR) is used to amplify a DNA fragment (4)
- Requires DNA polymerase, nucleotides and primers
- Heat to 95°C to break hydrogen bonds
- Reduce temperature so primers can bind to DNA
- Increase temperature so DNA polymerase joins nucleotides together
Why is the DNA heat to 95°C during PCR? (2)
- Produce single stranded DNA
- Breaks WEAK hydrogen bonds between strands
Why do you add primers during PCR? (3)
- Attaches to / complementary to start of the gene
- Replication of base sequence from here
- Prevents strands annealing
Explain why ‘base-pairs’ is a suitable unit for measuring the length of a piece of DNA. (3)
- DNA joined by linking of 2 bases / A with T and G with C
- Bases are a constant distance apart / nucleotides occupy constant distance
- Each base-pair is same length
Name three mutagenic agents (3)
- High energy radiation /ionising particles e.g. α, β
- Benzene
- X-rays
- UV (light)
- Carcinogen / named carcinogen
- Mustard gas / phenols / tar
Describe how a deletion mutation alters the structure of a gene. (2)
- Removal of one or more bases
- Frameshift/(from point of mutation) base sequence change
Describe the main stages in the copying, cutting and separation of the DNA. (6)
- Heat DNA to 95°C
- Strands separate
- Cool so that primers bind to DNA
- Add DNA polymerase/nucleotides
- Use of restriction enzymes to cut DNA at specific base sequence/ breaks phosphodiester bonds
- Use of electric current and agar/gel
- Shorter fragments move further
Describe the polymerase chain reaction. (6)
- Heat DNA
- Breaks hydrogen bonds/separates strands
- Add primers
- Add nucleotides
- Cool
- Binding of nucleotides/primers
- DNA polymerase
- Role of (DNA) polymerase
- Repeat cycle many times
Describe a plasmid. (3)
- Circular DNA
- Separate from main bacterial DNA
- Contains only a few genes
Suggest one reason why DNA replication stops in the polymerase chain reaction. (2)
- Limited number of primers/nucleotides
- DNA polymerase (eventually) denatures
Suggest why the restriction enzyme has cut the human DNA in many places but has cut the plasmid DNA only once. (3)
- Enzymes only cut DNA at specific base sequence/recognition site
- Sequence of bases/recognition site
- Occurs once in plasmid and many times in human DNA
(max 1 if no reference to base sequence OR recognition site)
Describe how the bacteria containing the insulin gene are used to obtain sufficient insulin for commercial use. (2)
- Use of fermenters
- Provides nutrients plus suitable conditions for optimum growth/named …
- Environmental factor
- Reproduction of bacteria
- Insulin accumulates and is extracted
Explain what is meant by a vector. (3)
- DNA Carrier
- Used to transfer foreign DNA
- Into cell/other organism
Explain how modified plasmids are made by genetic engineering and how the use of markers enable bacteria containing these plasmids to be detected. (6)
- Isolate TARGET gene/DNA from another organism
- From cell/organism
- Using restriction endonuclease enzyme
- To get DNA
- Produce sticky ends
- Use DNA ligase to join TARGET gene to plasmid
- Also include marker gene
- Example of marker e.g. antibiotic resistance
- Add plasmid to bacteria to grow (colonies)
- (replica) plate onto medium where the marker gene is expressed
- Bacteria not killed have antibiotic resistance gene and the TARGET gene
- Bacteria expressing the marker gene have the TARGET gene as well
mRNA may be described as a polymer. Explain why. (1)
- Made up of many (similar) molecules/monomers/nucleotides
