Variation

• Variation


  The phenotype an organism has depends on its genotype and environment
• The combining of genes from the mother and father creates genetic variation
• There is lots of genetic variation in a population
• Environment


  The place the organism lives in and the conditions it grows and develops in affects its appearance
• Characteristics can result from a combination of genetics and environment, such as weight
• Genetic variation


  Is introduced by mutations in the sequence of DNA
• Some mutations have no effect on the phenotype, some influence the phenotype but it is unlikely to bring about a new phenotype, and if the mutation does determine the phenotype and it is advantageous, natural selection will mean it becomes the common phenotype relatively quickly
• Selective breeding


  When humans choose which organisms to breed in order to produce offspring with a certain desirable characteristic
• Selective breeding has been happening for many years since animals were domesticated and plants were grown for food
• Selective breeding


  Parents with desired characteristics are chosen, the offspring with the desired characteristics are bred together, and this process is repeated many times until all the offspring have the desired characteristic
• Inbreeding


  The problem with selective breeding is that it can lead to inbreeding, which results in a reduction of the gene pool and a greater chance of genetic defects being present in the offspring
• Genetic engineering


  Modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic
• Genetic engineering process


  Genes are cut from chromosomes using restriction enzymes, leaving 'sticky ends'

  2. A plasmid is cut using the same restriction enzyme to also create sticky ends

  3. The gene and plasmid are joined together by DNA ligase enzymes

  4. The combined plasmid is put into a bacterial cell, which then grows and produces the modified gene
• Genetically Modified crops


  • They are engineered to be resistant to insects and herbicides, resulting in increased yields as less crops will die
• Gene therapy


  Using genetic engineering to cure genetic disorders by transferring genes into patients so they produce the correct proteins
• Perceived benefits of genetic engineering

  • Useful in medicine to mass produce certain hormones

  Can improve agricultural yields by introducing modifications

  Can produce useful substances that are difficult to obtain

  Can help solve world hunger
• Perceived risks of genetic engineering


  • GM crops may have unintended effects on wild insects and plants

  GM crops may lead to increased resistance in pests and weeds

  We may not fully understand the effects of GM crops on human health

  Genetic engineering in agriculture could lead to genetic engineering in humans