Cloning in plants

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  • Created by: Raachel
  • Created on: 26-02-14 11:36
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  • Cloning in Plants
    • natural vegetative propagation
      • refers to the production of structures in an organism that can grow into new individual organisms. these offspring contain the same genetic information as the parent so are clones of the parent.
      • The English Elm is adapted to reproduce asexually following damage to the parent plant
        • New growth in the form of basal sprouts appears within two months of the destruction of the maintrunk
        • These suckers grow from meristem tissue in the trunk close to the ground where the least damageis likely to have occurred
        • suckers grow into a circle of new elm trees called a CLONAL PATCH
      • no genetic variation within cloned population, so natural selection cannot occur
    • artificial vegetative propagation
      • cuttings
        • a section of stem is cut between leaf joints (nodes) and the cut end of the stem is then treated with plant hormones to encourage root growth, and planted
        • a new plant = a clone of the original parent plant
      • grafts
        • shoot section of woody plant is is joined to an already growing root (rootstock)
        • graft grows; it is genetically identical to the parent plant, but not to the rootstock
      • tissue culture
        • refers to the separation of cells of any tissue type and their growth in or on a nutrient medium.
        • PGR = plant growth regulators
        • steps (micro-propagation)
          • 4. After a few weeks, single callus cells can be removed and placed on a growth medium à PGR à encourage shoot growth
          • 3. Cells in the tissue divide but do not differentiate. Mass = callus
          • 5. After a few weeks, shoots transferred onto a DIFFERENT growing medium containing different PGR concentrations à encourage root growth
          • 2. It is placed in a nutrient growth medium containing high levels of auxins and cytokinin as wll as nitrates and phosphates.
          • 6.Plants transferred to a greenhouse to be acclimatised and grown further then planted outside
          • 1. A small piece of tissue is taken from the plant to be cloned, usually from the shoot tip. This is called an explant. (sterilised: bleach) 
    • asexual reproduction:      reproduction without the fusion of gamete, resulting in the offspring being a clone of the parent due to no exchange of genetic material
      • advantages:   -its quick         -can be completed if sexual reproduction fails                 -offspring have genetic info to enable them to survive
      • disadvantages: no genetic variation (reduces gene pool) therefore all susceptible to same disease

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