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Flashcards · Biology · Feeding the Human Race

The Steps of Genetic Engineering (Higher tier)

18 cards

  1. What does a restriction enzyme do?

    Cuts DNA at a specific sequence of bases.

  2. What are sticky ends?

    Short stretches of unpaired bases left at the ends of cut DNA, which can pair with matching ends.

  3. Why is the same restriction enzyme used to cut the gene and the plasmid?

    So that their sticky ends are complementary and can pair.

  4. Which bases would pair with the sticky end A-A-T-T?

    T-T-A-A.

  5. What does DNA ligase do?

    It joins the DNA strands, sealing the gene into the plasmid.

  6. What is recombinant DNA?

    DNA made by joining DNA from two different sources.

  7. What is a vector?

    A carrier, such as a plasmid, that takes a gene into a host cell.

  8. What is a plasmid?

    A small circular loop of DNA in bacteria, separate from the main chromosome.

  9. Why are bacteria used as hosts?

    They are simple, they reproduce very quickly and they can be grown cheaply in fermenters.

  10. Do all the bacteria take up the plasmid?

    No, only a small fraction do.

  11. What is an antibiotic resistance marker?

    A gene on the plasmid that lets the bacteria that carry it survive an antibiotic.

  12. How does the antibiotic select the right bacteria?

    Bacteria without the plasmid are killed or cannot grow, while those with it survive.

  13. What is a colony?

    A visible group of identical bacteria grown from one cell on agar.

  14. Where do restriction enzymes come from naturally?

    Bacteria, which use them to cut up the DNA of viruses.

  15. What is the final step after selection?

    The selected bacteria are grown in a fermenter, where they multiply and make the protein.

  16. Why does ligase matter?

    Without it the gene could fall out of the plasmid again.

  17. Six panels showing DNA being cut, joined, put into a bacterium, selected and grown, with no labels. Describe what is happening in each of the six steps. The same six panels with the sticky end, plasmid, marker gene, gene, host bacterium, colony, agar and protein labelled.

    1 A restriction enzyme cuts out the gene, leaving sticky ends. 2 The same enzyme cuts the plasmid. 3 DNA ligase joins the gene into the plasmid. 4 The plasmid enters the host bacterium. 5 Only bacteria with the resistance marker grow on antibiotic agar. 6 The bacteria multiply and make the protein.

  18. The six-step diagram with a sticky end marked A, a plasmid marked B and a host bacterium marked C. Name the parts marked A, B and C.

    A is a sticky end. B is a plasmid (the vector). C is the host bacterium.