Genetic engineeringIB MYP Biology: Revision notes
Section 1
What is genetic engineering?
Genetic engineering (genetic modification, GM) means changing the genes of an organism by taking a gene from one organism and inserting it into another. The new organism is a genetically modified organism (GMO).
It works because the genetic code is the same in all living things. A gene from a human, a plant or a bacterium is read in the same way by the cells of another organism, so the host can make the protein the gene codes for.
Section 2
The steps
Genetic engineering follows these steps:
- Identify the gene that gives the useful characteristic.
- Cut the gene out of the DNA using restriction enzymes.
- Insert the gene into a vector, such as a plasmid or a virus (cut with the same enzyme so the ends fit).
- The vector transfers the gene into the host cell (a bacterium, plant or animal cell).
- The host cell expresses the gene, making the protein. The cells divide, or grow into whole organisms, which are tested.
Learn the steps in order: identify, cut, insert, transfer, express.
Section 3
Example 1: human insulin
People with diabetes need insulin. The human insulin gene is cut out using restriction enzymes and inserted into a bacterial plasmid. The plasmid is put into bacteria, which are grown in large fermenters. The bacteria reproduce rapidly and make human insulin, which is purified.
Benefits: large amounts can be made cheaply, it is identical to human insulin, and no animals are needed.
Section 4
Example 2: Bt crops
Bt crops, such as Bt cotton and Bt maize, contain a gene from the soil bacterium Bacillus thuringiensis. The gene makes a protein that is toxic to certain insect pests, such as bollworm caterpillars.
Benefits: less crop is lost and farmers need to spray less insecticide. Concerns: insects may develop resistance, other insects may be harmed, and the seed can be expensive.
Section 5
Example 3: golden rice
Golden rice has been engineered with genes from a plant and a bacterium so that the grains make beta-carotene, which the body turns into vitamin A. It is intended to prevent vitamin A deficiency, a cause of blindness in children in countries where rice is the main food.
Benefits: it could save sight and lives. Concerns: unknown long-term effects, cost, and some people's objections to GM food.
Section 6
Benefits and concerns
Benefits: higher yields, crops that resist pests or drought, added nutrients, and cheap medicines.
Concerns: possible long-term effects on health and the environment, genes spreading to wild relatives, companies controlling seed, and ethical objections.
For a discussion answer, give both sides and finish with a justified conclusion.
Do not say GM crops are 'unnatural so unsafe' without a reason. Name a specific concern such as gene spread or unknown long-term effects.
That's the notes covered.
Carry on to the next subtopic.
Exam questions on Genetic engineering
- Millions of people with diabetes need regular injections of insulin. Insulin used to be extracted from the pancreases of pigs and cattle. A biotechnology company in India now makes human insulin using genetically modified bacteria grown in large steel fermenters. The human insulin gene is cut out of human DNA and inserted into a bacterial plasmid, which is then put into the bacteria.Explain why bacteria are suitable organisms for making human insulin.2 marks
- Farmers in Burkina Faso compared two types of cotton in a field trial. Bt cotton contains a gene from the bacterium Bacillus thuringiensis, which makes a protein that is toxic to bollworm caterpillars. Conventional cotton does not contain this gene. Two plots of the same size were sown on the same day in the same field, with the same soil, water and fertiliser. At harvest, 100 plants were chosen at random from each plot and the number of damaged cotton bolls was counted. In the conventional plot there were 46 damaged bolls and in the Bt plot there were 7.Suggest two ways in which the farmers could improve the reliability of this trial.2 marks
- In parts of Asia and Africa, many children who eat mainly rice become short of vitamin A, which can cause blindness. Scientists produced 'golden rice' by adding genes from a plant and a bacterium to rice. The genes allow the rice grains to make beta-carotene, which the body converts to vitamin A. The grains are golden in colour.Outline the main steps in producing golden rice.3 marks
Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).