Once a recombinant plasmid carrying the human insulin gene has been made, it must be taken up by a bacterium before any insulin can be produced. The diagram...
Question 1 Report
Once a recombinant plasmid carrying the human insulin gene has been made, it must be taken up by a bacterium before any insulin can be produced. The diagram shows a single bacterium taking up one of these recombinant plasmids. Two parts of the bacterium are labelled X and Y. Inside the bacterium the plasmid carries the added human gene, which the bacterium can read and use in the same way as its own genes. Bacteria treated in this way can then be grown in very large numbers, so that each one makes the human protein. This makes bacteria a convenient and plentiful source of insulin for people who have diabetes.
(a) Using the diagram, name the parts labelled X and Y. [2]
(b) Describe how the bacterium uses the recombinant plasmid to make insulin. [2]
(c) Explain why bacteria are suitable organisms for producing large amounts of insulin. [3]
(d) State two advantages of treating patients with insulin from genetically modified bacteria rather than with insulin extracted from animals. [2]
Answer Details
This question tests recombinant DNA technology - using bacteria to manufacture human insulin.
- Naming X and Y [2]. X is the bacterial (chromosomal) DNA, the single circular loop of the cell's own genetic material [1]. Y is the (recombinant) plasmid, the small extra circle of DNA that has been given the human insulin gene [1].
- How the plasmid is used to make insulin [2]. The human insulin gene on the plasmid is transcribed (read) by the bacterium's enzymes just like its own genes [1]; the instructions are then translated so the bacterium builds the insulin protein [1]. The key idea is that the genetic code is universal, so a human gene works inside a bacterial cell.
- Why bacteria are suitable [3]. Bacteria divide very rapidly, so huge numbers are produced in a short time [1]; every daughter cell inherits a copy of the plasmid and its gene, so all of them make insulin [1]; and they can be grown cheaply on a simple nutrient medium in a fermenter [1].
- Advantages over animal insulin [2, any two]. The insulin is identical to human insulin, so there is less risk of an allergic reaction or rejection; large amounts can be made quickly and more cheaply; and no animals need to be killed to obtain it. Any two.
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