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Natural Selection and Genetic Modification

The stages of genetic engineering

  • 3 things to know
  • Paper 1

Overview

Restriction enzymes and sticky ends, why the gene and vector are cut with the same enzyme, ligase, plasmids and viruses as vectors, the stages of inserting a human gene into a bacterium, recombinant plasmids, and why bacteria make useful host cells.

What you need to know

Answer each one before you reveal it.

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Process

Describe the main stages in inserting a human gene into a bacterium.

Key term

Explain why the gene and the vector must be cut with the same restriction enzyme.

Key term

What name is given to a plasmid that has had DNA from another organism joined into it?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What is the role of a restriction enzyme in genetic engineering?

    Model answer

    It cuts DNA at a specific sequence of bases, which is how the required gene is cut out of the donor DNA.

  2. 2

    What is a sticky end?

    Model answer

    It is the short run of unpaired bases on a single strand left overhanging at the point where a restriction enzyme has cut the DNA.

  3. 3

    Explain why the gene and the vector must be cut with the same restriction enzyme.

    Model answer

    The one enzyme leaves sticky ends with complementary base sequences, so the bases on the gene's ends will pair with those on the vector's ends.

  4. 4

    What is the role of ligase in genetic engineering?

    Model answer

    It joins the sugar-phosphate backbones of the inserted gene and the vector, sealing them into one continuous piece of DNA.

  5. 5

    What is a vector in genetic engineering?

    Model answer

    It is a piece of DNA, usually a bacterial plasmid or a virus, that carries the inserted gene into the host cell.

  6. 6

    Describe the main stages in inserting a human gene into a bacterium.

    Model answer

    A restriction enzyme cuts the gene out of the human DNA, the same enzyme cuts open a plasmid, the matching sticky ends pair up and ligase seals them, and the plasmid is then taken up by the bacterium.

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Key Concepts in Biology
Cells and Control
Genetics
Natural Selection and Genetic Modification

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