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KS4 Genetics, GM & Cloning
6.3.3 The understanding of genetics
- know that in the mid-19th century Gregor Mendel carried out breeding experiments on plants and that one of his observations was that the inheritance of each characteristic is determined by ‘units’ that are passed on to descendants unchanged.
- Know that in the late 19th century behaviour of chromosomes during cell division was observed.
- Know that in the early 20th century it was observed that chromosomes and Mendel’s ‘units’ behaved in similar ways, leading to the idea that the ‘units’, now called genes, were located on chromosomes.
- Know that in the mid-20th century the structure of DNA was determined and the mechanism of gene function worked out.
- Know that this scientific work by many scientists led to the gene theory being developed, but that the importance of Mendel’s discovery was not recognised until after his death.
6.2.3 Selective breeding
- Know that selective breeding (artificial selection) is the process by which humans breed plants and animals for particular genetic characteristics.
- Know that Humans have been using selective breeding for thousands of years since they first bred food crops from wild plants and domesticated animals.
- Know that selective breeding involves:
- choosing parents with the desired characteristic from a mixed population.
- They are bred together.
- From the offspring those with the desired characteristic are bred together.
- This continues over many generations until all the offspring show the desired characteristic.
- Know that the characteristic can be chosen for usefulness or appearance, for example:
- Disease resistance in food crops.
- Animals which produce more meat or milk.
- Domestic dogs with a gentle nature.
- Large or unusual flowers.
- That selective breeding can lead to ‘inbreeding’ where some breeds are particularly prone to disease or inherited defects, for example some breeds of dogs suffer from frequent defects.
- Be able to explain the benefits and risks of selective breeding given appropriate information and consider related ethical issues.
6.2.4 Genetic engineering
- Know that genetic engineering is a process that involves modifying the genome of an organism by introducing a gene from another organism to give the desired characteristic.
- Know that plant crops have been genetically engineered to be resistant to diseases or to produce bigger better fruits.
- Know that bacterial cells have been genetically engineered to produce useful substances such as human insulin to treat diabetes.
- Know that in genetic engineering, genes from the chromosomes of humans and other organisms can be ‘cut out’ and transferred to cells of other organisms.
- Know that crops that have had their genes modified in this way are called genetically modified (GM) crops.
- Know that GM crops include ones that are resistant to insect attack or to herbicides.
- Know that GM crops generally show increased yields because of the characteristics chosen such as larger fruits, disease resistance or herbicide resistance.
- Know that concerns about GM crops include the effect on populations of wild flowers and insects and that some people feel the effects of eating GM crops on human health have not been fully explored.
- Know that modern medical research is exploring the possibility of genetic modification to overcome some inherited diseases.
- Be able to explain the potential benefits and risks of genetic engineering in agriculture and in medicine and that some people have ethical objections.
- Be able to describe the main steps in the process of genetic engineering, including: (HT only)
- enzymes are used to isolate the required gene; this gene is inserted into a vector, usually a bacterial plasmid or a virus
- the vector is used to insert the gene into the required cells
- genes are transferred to the cells of animals, plants or microorganisms at an early stage (egg or embryo) in their development so that they develop with desired characteristics.
- Be able to interpret information about genetic engineering techniques and to make informed judgements about issues concerning cloning and genetic engineering, including GM crops.
- Know that tissue culture is the process of using small groups of cells from part of a plant to grow identical new plants.
- Know that tissue culture is important for preserving rare plant species or commercially in nurseries.
- Know that cuttings is an older, but simple, method used by gardeners to produce many identical new plants from a parent plant.
- Know that embryo transplants is the process of splitting apart cells from a developing animal embryo before they become specialised, then transplanting the identical embryos into host mothers.
- Know the process of adult cell cloning:
- the nucleus is removed from an unfertilised egg cell.
- The nucleus from an adult body cell, such as a skin cell, is inserted into the egg cell.
- An electric shock stimulates the egg cell to divide to form an embryo.
- These embryo cells contain the same genetic information as the adult skin cell.
- When the embryo has developed into a ball of cells, it is inserted into the womb of an adult female to continue its development.
- Be able to explain the potential benefits and risks of cloning in agriculture and in medicine and that some people have ethical objections.
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