Genetic Manipulation
Visão Geral
Somewhere in a laboratory, a single gene is lifted out of the chromosomes of one species and dropped into the cells of another. The organism that receives it goes on to grow a characteristic that nothing in its ancestry could ever have given it: a maize plant that poisons the caterpillars feeding on it, a crop that shrugs off a weedkiller which flattens everything green around it. Nothing about the plant is a copy of anything. One instruction has been added, and the rest of the organism is exactly as it was.
This lesson follows that single gene the whole way: out of one chromosome, into a carrier, through a cell wall and into a crop growing in a field. You will learn the three stages the specification asks you to name, why the timing of the transfer decides whether the characteristic shows up in one leaf or in all of them, what genetically modified crops are actually built to do, and why the arguments about them are still running. That last part carries marks of its own: OxfordAQA expects you to read information you have never seen before about genetic engineering and reach a judgement you can defend from it.
Objetivos
- In genetic engineering, genes from the chromosomes of humans and other organisms can be ‘cut out’ and transferred to cells of other organisms: enzymes are used to isolate the required gene; this gene is inserted into a vector, usually a bacterial plasmid or a virus 38 ; the vector is used to insert the gene into the required cells.
- Genes can also be transferred to the cells of animals, plants or microorganisms at an early stage in their development so that they develop with desired characteristics.
- Crops that have had their genes modified in this way are called genetically modified (GM) crops. GM crops include ones that are resistant to insect attack or to herbicides.
- GM crops generally show increased yields.
- Concerns about GM crops include the effect on populations of wild flowers and insects, and uncertainty about the effects of eating GM crops on human health. Students should be able, when provided with appropriate information, to interpret information about genetic engineering techniques and to make informed judgements about issues concerning genetic engineering, including GM crops.
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Use esta secção de avaliação como uma oportunidade para reforçar a tua compreensão do tema e identificar quaisquer áreas onde possas precisar de estudo adicional. Não te deixes desencorajar pelos desafios que encontrares; em vez disso, vê-os como oportunidades de crescimento e melhoria.
- In genetic engineering, what is usually used as a vector? A. A ribosome B. A red blood cell C. A bacterial plasmid D. A chromosome pair Answer: C
- What is used to isolate the required gene from a chromosome in genetic engineering? A. Enzymes B. A herbicide C. An electric shock D. A mineral ion solution Answer: A
- Which of these is a plasmid? A. A small circle of DNA in the cytoplasm of a bacterium B. A structure that joins two chromosomes together C. A gamete produced by a flowering plant D. A substance that kills insect larvae Answer: A
- A GM crop is described as herbicide resistant. What does this allow the farmer to do? A. Harvest the crop before it is ripe B. Spray the field so that the weeds die but the crop survives C. Grow the crop without any mineral ions in the soil D. Produce identical copies of the crop plant Answer: B
- Which of these is a concern raised about growing GM crops? A. GM crops generally give lower yields B. GM crops cannot be resistant to herbicides C. GM crops may affect populations of wild flowers and insects D. GM crops contain no genes of their own Answer: C
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