Why are organisms different?

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  • Why are organisms different?
    • Genes give offspring similar characteristics to their parents- passed on by gametes
      • The nucleus of a cell contains chromosome. Chromosomes carry genes that control the characteristics of the body
    • Differences in characteristics are caused by...
      • Environmental factors eg  accent, relgion etc
      • Genetic factors eg height, eye colour, metabolism etc
      • Both eg weight, hair colour
    • Reproduction
      • Sexual reproduction- egg and sperm cell fuse. Mixture of genetic info from both gametes leads to variabtion
      • Asexual reproduction- one parent, no mixing of genes, no variation = clones
    • Plants can be cloned by taking a cutting and sticking it in a rooting compound (hormone)
      • This will encourage roots to grow
    • Modern cloning techniques
      • Tissue Culture (plants)
        • Cells taken from parent plant. Put in nutrient agar. Small clone plants grow.
      • Embryo Transplant (animals)
        • Fertilize egg cell. The cells grow to become an embryo (ball of unspecialised cells) The embryo is split into multiple balls of cells. Then implanted into host mother.
      • Adult Cell Cloning
        • 1) Take skin cell from sheep A (take you want to clone)
          • 2) Take egg cell from sheep B
            • 3) Insert the nucleus of sheep A cell into empty sheep B cell.
              • 4) Give cells an electric shock to stimulate growth.
                • 5) Implant egg cell into sheep C (host mother)
    • Genetic engineering- transfer of genes
      • Desirable genes can be "cut out" of chromosomes by enzymes and  transferred to cells of other organisms
      • Crops that have had their genes modified are called genetically modified crops (GM crops)
        • GM crops have increased yields, useful for feeding a growing population.
        • There are concerned about the effect of GM crops on wild flowers and insects and whether eating GM food may harm human health.


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