DNA technology

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  • Created by: LZ95
  • Created on: 15-04-14 15:14
What does the enzyme 'reverse transcriptase' do?
Catalyses the production of DNA from RNA (reverse of transcription)
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What strand does mRNA make?
A cDNA strand (nucleotides complementary to mRNA)
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Which enzyme builds up the second strand of DNA which is complementary to cDNA?
DNA polymerase
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What is a restriction endonuclease?
Enzyme that cuts up viral DNA
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Where does a restriction endonuclease cut DNA?
At a specific sequence of bases called a recognition sequence
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Name the two types of ends that restriction endonucleases can leave
Blunt ends and sticky ends
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What does it mean when the nucleotides left exposed on two strands are palindromes of each other?
They are the opposites of each other e.g. AGGCTT and TTCGGA
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What does in vivo cloning involve?
Transferring fragments to a host cell using a vector
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What does in vitro cloning involve?
Using the polymerase chain reaction
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What enzyme joins together the complementary bases of two sticky ends?
DNA ligase
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How does this enzyme do this?
By joining together the phosphate-sugar framework of the two sections of DNA
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What is a vector?
A carrying unit for DNA
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What is the most common vector?
A plasmid
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How are plasmids introduced into host cells?
Plasmids + bacterial cells mixed in a medium containing calcium ions. The ions + changes in temperature make bacteria permeable allowing plasmids to pass through the cell membrane into the cytoplasm.
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Give 2 reasons why not all bacterial cells will possess DNA fragments
1. Only a few bacterial cells take up plasmids when they are mixed together 2. Some plasmids close up without joining with DNA fragments
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How is the knowledge of the fact that bacteria carry genes for antibiotic resistance helpful in determining which bacterial cells have taken up the plasmid?
Bacterial cells can be grown on a medium containing ampicillin. The bacterial cells which have taken up the plasmid will break down ampicillin and survive, where those that haven't will die as they are not resistant.
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What is used to determine which bacteria have taken up plasmids that contain the required gene?
Gene markers
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Name 3 ways in which a gene marker may be easily identifiable
1. It may be resistant to an antibiotic 2. It may make a fluorescent protein 3. It may produce an enzyme whose actions can be identified.
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What is meant by replica plating?
Where cells are spread very thinly on a nutrient agar plate and form identical colonies. Samples from each colony are put onto a replica plate in the same position, only difference is this plate contains the second antibiotic in the plasmids.
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How would you know a cell has taken up the plasmid with the new gene inside?
The new gene would have replaced the gene for antibiotic resistance to the second antibiotic, so these cells would be killed on the replica plate.
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What gene do fluorescent markers use?
A gene from a jellyfish which produces a green fluorescent protein.
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When using fluorescent markers, what would scientist look for when determining which bacterial cells have taken up the new gene?
Cells that are not fluorescent as the bacterial cells with the new gene will not be fluorescent as the new gene is transplanted into the middle of the GFP gene
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What enzyme is used when using enzyme markers?
Lactase
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How is this used?
New gene is transplanted into the gene that makes lactase so bacteria can no longer make lactase, so when they are grown on a colourless substances they cannot change its colour (whereas with lactase it would turn blue)
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Name 5 things that the polymerase chain reaction requires
DNA fragment to be copied, DNA polymerase, primers, nucleotides and a thermocycler
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What are primers?
short sequences of nucleotide that have a set of bases complementary to those at one end of each of the two DNA fragments
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What is a thermocycler?
A computer controlled machine that varies temperatures precisely over a period of time.
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What are the 3 stages in PCR?
Separation of the DNA strand, addition of primers and DNA synthesis
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What cause the two strands of DNA to separate?
The thermocycler increasing the temperature to 95 Celsius
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Why is it important that primers are added?
They provide starting sequences for DNA polymerase to begin DNA copying as it can only attach nucleotides to the end of an existing chain.
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What are two advantages of in vitro gene cloning?
Extremely rapid + does not require living cells
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What are 3 advantages of in vivo gene cloning?
Very useful when introducing a gene into another organism, involves no risk of contamination, very accurate
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State 3 ways in which recombinant DNA technology can benefit humans
Increase yield from plants/animals, improves nutrient content of foods, production of vaccines, making crop plants tolerant to herbicides
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How can antithrombin be produced using genetically modified animals?
Gene for this protein added to fertilised eggs from a goat along with gene coding for protein in goats milk. This means goats will produce milk rich in antithrombin and this can be extracted and given to patients.
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Name 3 advantages of recombinant DNA technology
Drugs antibiotics + enzymes can be produced, GM crops can be grown in countries with extreme conditions, gene fingerprinting used in forensics
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Name 3 disadvantages of recombinant DNA technology
Engineered gene could mutate into a pathogen, can disturb ecology by introducing GM organisms, could lead to cancer, may get into the wrong hands
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Other cards in this set

Card 2

Front

What strand does mRNA make?

Back

A cDNA strand (nucleotides complementary to mRNA)

Card 3

Front

Which enzyme builds up the second strand of DNA which is complementary to cDNA?

Back

Preview of the front of card 3

Card 4

Front

What is a restriction endonuclease?

Back

Preview of the front of card 4

Card 5

Front

Where does a restriction endonuclease cut DNA?

Back

Preview of the front of card 5
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