The shape of the lesson
By the end of the lesson, learners can
- What genetic modification is: Press Next step to work through how bacteria are made to produce human insulin, then use the GM crop chips (herbicide resistance, insect resistance, nutrition) to see the plant examples.
- Cut, paste, multiply: Extended.
- GM crops: for and against: Extended.
- Definition: removing, changing or inserting individual genes.
- Restriction enzymes cut, leaving sticky ends; use the same enzyme on gene and plasmid.
- DNA ligase joins, forming a recombinant plasmid; bacteria then multiply and express the gene.
- Crop examples: herbicide resistance, insect resistance, improved nutrition (golden rice).
One picture every idea returns to
Genetic modification is changing the genetic material of an organism by removing, changing or inserting individual genes. Examples: human genes inserted into bacteria to produce human proteins such as insulin; genes inserted into crop plants to give resistance to herbicides or insect pests, or to improve nutritional qualities. Extended: a human gene is cut out with restriction enzymes, leaving sticky ends; a plasmid is cut with the same enzyme; DNA ligase joins them into a recombinant plasmid, which is put into bacteria that multiply and express the gene.
Forty-five minutes, phase by phase
| Time | Phase | What happens in the room | Grouping |
|---|---|---|---|
| 0 to 5 min | Hook: predict | Open with the question in the title, Moving a gene between species.. Genetic modification changes an organism's genetic material one gene at a time. Put the figure on the board: it is the one picture every idea in the lesson returns to. | Whole class, then pairs |
| 5 to 13 min | Teach and check: What genetic modification is | Press Next step to work through how bacteria are made to produce human insulin, then use the GM crop chips (herbicide resistance, insect resistance, nutrition) to see the plant examples. Project tab 7 of the lab (Genetic modification of bacteria and crops) and let a student drive it while the class predicts. | Whole class, then pairs |
| 13 to 21 min | Teach and check: Cut, paste, multiply | Extended. | Pairs |
| 21 to 30 min | Teach and check: GM crops: for and against | Extended. | Frayer Model |
| 30 to 36 min | Check | The four Stage 1 questions from the student lesson, answered on mini whiteboards or by show of fingers. Re-teach the one most get wrong. | Individual, then whole class |
| 36 to 43 min | Plenary | The exam-style questions from Stage 2, one at a time: thirty seconds alone, then a random call. The feedback lines in the key give the examiner's wording. | Individual, random call |
| 43 to 45 min | Exit and homework | Set the worksheet below (6 questions, 23 marks). Learners self-assess against the objectives before they leave. | Individual |
Protect the parts that carry the learning
The sequence carries about fifty minutes of material, so the lab is driven by one student while the class predicts rather than explored freely. Times are a guide.
Protected: the check at 30 minutes. It is the only individual read on whether the key idea landed, and it is not cut.
Cut first if the build overruns: the last check in GM crops: for and against, never the check or the plenary.
In a 60 minute block: run worksheet questions 1 to 3 in class as a Rally Coach set and model both the hardest worked example and its check live.
Frayer Model
Pairs fill a four-box grid for the key term: definition, characteristics, examples and non-examples. The non-examples box is where the misconceptions surface, so give it the most time.
The full structure, with its variations and the other twelve, is on the cooperative-learning page.
What to head off, and how
| Trap learners fall into | Teaching move that pre-empts it |
|---|---|
| Genetic modification is not the same as selective breeding. | Selective breeding mixes whole sets of genes over many generations; genetic modification moves or changes individual genes, often between different species. |
| Restriction enzymes cut DNA; DNA ligase joins it. | The same restriction enzyme must cut both the gene and the plasmid, or the sticky ends will not be complementary. |
| In a 'discuss' question give both sides: at least one advantage and one disadvantage, each linked to a named crop where you can (soya, maize, rice). | Return to GM crops: for and against: ask a pair to state the correct version and show it on the lab before moving on. |
Genetic modification: worksheet
6 questions, 23 marks. Written in the style of the papers; no past paper question is reproduced.
Define genetic modification and give three examples of its use.
Extended. Outline how bacteria can be genetically modified to produce human insulin.
Extended. Explain what is meant by sticky ends and why they are useful.
Describe how genetic modification has been used to make crop plants resistant to insect pests, and state one benefit to the farmer.
Extended. Discuss the advantages and disadvantages of growing genetically modified crops such as soya, maize and rice.
Extended. Before genetically modified bacteria were used, people with diabetes were treated with insulin extracted from the pancreas of pigs and cattle. Suggest three advantages of using insulin from GM bacteria.
Answer key and marking notes
- Changing the genetic material of an organism by removing, changing or inserting individual genes.
- Inserting human genes into bacteria to produce human proteins such as insulin.
- Inserting genes into crop plants to give resistance to herbicides or to insect pests.
- Inserting genes into crop plants to improve their nutritional qualities, such as golden rice with extra vitamin A.
- The human insulin gene is cut out of human DNA using restriction enzymes, forming sticky ends.
- A bacterial plasmid is cut with the same restriction enzymes, forming complementary sticky ends.
- The insulin gene is inserted into the plasmid and joined using DNA ligase, forming a recombinant plasmid.
- The recombinant plasmids are inserted into bacteria.
- The bacteria multiply rapidly (in a fermenter), copying the plasmid.
- The bacteria express the human gene and make human insulin, which is extracted and purified.
- Short single-stranded sections of DNA left at the ends of a cut DNA molecule by a restriction enzyme.
- Their bases are complementary to the sticky ends on the plasmid cut by the same enzyme, so the two can pair before DNA ligase joins them.
- A gene (from a bacterium) is inserted into the crop plant, such as maize.
- The plant makes a toxin that kills insect pests that eat it.
- Benefit: less crop damage, so a higher yield, and less insecticide needs to be bought and sprayed.
- Advantage: higher yields because less crop is lost to weeds (herbicide-resistant soya, maize) or insect pests (insect-resistant maize).
- Advantage: less insecticide sprayed; golden rice could reduce vitamin A deficiency.
- Disadvantage: GM seed is expensive and may need to be bought every year, which is hard for poor farmers.
- Disadvantage: genes may spread to wild relatives, producing herbicide-resistant weeds; herbicide use may increase; insects that are not pests may be harmed.
- Disadvantage: reduced biodiversity, and concern about unknown long-term effects on health. (A balanced answer with a conclusion gains credit.)
- It is human insulin, so it is identical to the patient's own and less likely to cause an immune reaction.
- Large amounts can be made quickly and cheaply because bacteria reproduce rapidly in fermenters, so supply meets demand.
- No animals need to be slaughtered, so there are fewer ethical or religious objections, and no risk of passing on animal diseases.
8 multiple-choice questions on this lesson
From the topic question bank. Assign them in the app for a marked score in your gradebook, or run the topic as a class game.
Which of these is an example of genetic modification?
- AInserting a gene into maize so that it makes a toxin that kills insect pests
- BBreeding the two highest-yielding wheat plants together for ten generations
- CTaking cuttings from a rose plant to grow identical new plants
- DSpraying a crop with insecticide to kill insect pests
A farmer grows herbicide-resistant soya. What is the main benefit to the farmer?
- AHerbicide can be sprayed to kill weeds without harming the soya
- BThe soya makes its own herbicide, so no spraying is needed
- CInsect pests that eat the soya are killed by the plant
- DThe soya beans contain extra vitamins that improve nutrition
Golden rice was genetically modified to improve its nutritional quality. Which deficiency is it intended to reduce?
- Avitamin A deficiency
- Bvitamin C deficiency (scurvy)
- Ciron deficiency
- Dprotein deficiency (kwashiorkor)
Bacteria that have been given the human insulin gene make human insulin. Why can the bacteria make a human protein?
- AThey read the inserted human gene to make the protein, just as human cells do
- BThey copy the insulin protein directly from a human cell
- CThey change their own chromosome into a human chromosome
- DThey absorb insulin from the nutrient solution in the fermenter
Extended: which statement is a disadvantage of genetically modified crops rather than an advantage?
- AGenes for herbicide resistance may spread to wild plants by pollen
- BLess insecticide is sprayed on insect-resistant maize
- CGolden rice could reduce a vitamin deficiency in poor countries
- DHigher yields are possible because fewer plants are lost to pests
Extended: a restriction enzyme cuts a plasmid and leaves the sticky end shown. Which sticky end on the cut human gene would pair with it?
- ATTAA
- BAATT
- CGGCC
- DCCGG
Extended: what is the role of DNA ligase in genetic modification?
- AIt joins the human gene into the cut plasmid to form a recombinant plasmid
- BIt cuts the human gene out of the DNA leaving sticky ends
- CIt carries the recombinant plasmid into the bacterial cell
- DIt makes the human protein from the instructions in the gene
Extended: put these steps for making human insulin in bacteria in the correct order. P: bacteria multiply. Q: plasmid cut with a restriction enzyme. R: recombinant plasmid inserted into bacteria. S: human gene and plasmid joined by DNA ligase.
- AQ, S, R, P
- BS, Q, R, P
- CQ, R, S, P
- DP, Q, S, R
Quiz key
Inserting a gene into maize changes its genetic material directly, which is genetic modification. Breeding the best plants over many generations is selective breeding. Cuttings produce clones by asexual reproduction without changing genes. Spraying insecticide changes nothing in the plant's DNA.
Because the soya survives the herbicide, the whole field can be sprayed and only the weeds die, so the crop has less competition and gives a higher yield. Herbicide-resistant crops do not make herbicide. Killing insect pests is the result of a different modification, insect resistance. Extra vitamins come from modifications to improve nutrition, such as golden rice.
Golden rice contains extra beta-carotene, which the body converts to vitamin A, to reduce vitamin A deficiency where rice is the main food. It was not modified to supply vitamin C, iron or extra protein, although those deficiencies also occur in poor diets.
The bacteria use the instructions in the human gene to make the same protein a human cell would make, because the genetic code is the same. Proteins are not copied directly from other proteins. Only one gene is added; the bacterial chromosome stays bacterial. The insulin is made inside the bacteria, not absorbed from the medium.
If pollen carries the herbicide resistance gene to related wild plants, herbicide-resistant weeds could appear, which is a disadvantage. Using less insecticide, reducing vitamin deficiency and higher yields are all advantages of GM crops.
A pairs with T and T with A, so the complementary sequence to AATT is TTAA, which is what the same restriction enzyme leaves on the other piece of DNA. AATT is identical rather than complementary, so its bases would not pair. GGCC and CCGG contain C and G, which cannot pair with A or T.
DNA ligase joins the sugar-phosphate backbones of the gene and plasmid once the sticky ends have paired, forming a recombinant plasmid. Cutting is done by restriction enzymes. Getting the plasmid into bacteria is a separate step and does not use ligase. The protein is made by the bacterium expressing the gene.
The plasmid is cut first (Q), then the gene is joined in by DNA ligase (S), the recombinant plasmid is put into bacteria (R) and the bacteria multiply (P). Joining before cutting (S first) is impossible. Inserting the plasmid into bacteria before joining (R before S) would put an empty plasmid in. Multiplying first (P) would grow bacteria without the gene.
What to project
The student lesson embeds these tabs. Open them full screen on the projector; every slider has a drag handle on the stage.
Slides for this lesson
A projectable deck for every pack is on the way. Until then, present the student lesson full screen: its sections, figure and lab tabs follow the same order as the plan above.