manipulating-genes

manipulating-genes - Manipulating genes Sir Ralph Riley 2...

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Manipulating genes © Sir Ralph Riley
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Ever since humans have been domesticating animals and raising crops they have been (unwittingly) manipulating genes By cross pollination and cross breeding they have tried to introduce the beneficial characteristics of one variety into a different variety of the same species* For example, a bull born to a cow that has a good milk yield, might be mated with a cow from a low-yielding stock, in the hope that the offspring will inherit the characteristics which lead to a high milk yield This has been done for thousands of years without any knowledge of genes or the mechanism of inheritance Cross breeding 2
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In the following (hypothetical) example, a variety of high yielding wheat which has poor resistance to disease… …is crossed with a variety which has good disease resistance but gives a poor yield The gene* for ‘high yield’ is represented by H The gene for ‘low yield’ is represented by h The gene for ‘good disease resistance’ is represented by R The gene for ‘poor disease resistance’ is represented by r Crossing 3
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HHrr high yield low resistance pollen grain ovule hhRR low yield high resistance The F 1 consists of plants with high yield and good resistance zygote 4
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Can you see any disadvantages in this method of manipulating genes ? Try working out what would happen if you tried to breed from the F 1 Work out the various gene combinations in the gametes Put them into a 4x4 Punnett Square 5
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F 1 cross HhRr x HhRr Possible combination of genes in gametes HR Hr hR hr HR Hr hR hr HR Hr hR hr HHRR HHRr HhRR HhRr HHRr HHrr HhRr Hhrr HhRR HhRr hhRR hhRr HhRr Hhrr hhRr hhrr The F 1 does not breed true. Of the 16 possible combinations of genes, 7 do not have the combined beneficial genes F 1 cross 6
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a b c d e a x b = c c x d = e Hybrid wheat ( c ) was crossed with wild wild grass ( d ) to give hybrid wheat ( e ) used for making flour and bread Manipulating genes by cross breeding Wheat variety ( a ) was crossed with wild grass ( b ) to give hybrid wheat ( c ) wheat © Sir Ralph Riley 7
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Interbreeding transfers the complete genome of one variety to another. This means that many new and unpredictable gene combinations may be formed in addition to those intended This method of genetic recombination can take place only between varieties of the same or closely related species Genetic engineering makes it possible to transfer single genes The genes can also be transferred from one species to a totally different species Genetic engineering 8
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There are several ways in which genes from one organism can be inserted into a different organism They can be coated on to microscopic gold particles and ‘fired’ into the cells They can be delivered by viruses They can be transmitted by using structures, called plasmids, present in bacteria For example, the human gene for making insulin can be transferred to bacteria, which are then allowed to reproduce in a culture medium from which the insulin can be extracted Plasmids 9
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This note was uploaded on 11/29/2011 for the course BIO 218 taught by Professor Young during the Fall '11 term at BYU.

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manipulating-genes - Manipulating genes Sir Ralph Riley 2...

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