Biotechnology and Gene Technologies

Unit 2

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  • Biotechnology and Gene Technologies
    • Artificial Clones and Agriculture
      • USED FOR YEARS Artificial vegetative propagation - two main methods:
        • Taking cuttings
          • Section of stem cut between leaf joints (nodes)
            • Cut end of stem often treated with plant hormones to encourage root growth and planted
              • Cuttings form new plant which is clone of original parent plant
        • Grafting
          • Shoot section of woody plant joined to an already growing root and stem (a rootstock)
            • Graft grows and is genetically identical to parent plant, but rootstock is genetically different
        • Cuttings and grafts cannot produce huge numbers of cloned plants very easily
        • Plants do not reproduce well from either cuttings or grafts
      • MODERN Artificial propagation using tissue culture: large-scale cloning
        • Tissue culture
          • Generate huge numbers of genetically identical plants from very small amount of plant material
          • Can be used to generate large stocks of a particularly vulnerable plant very quickly, with added advantage that these stocks known to be disease-free
        • Micropropagation by callus tissue culture
          • Most common method used in the large-scale cloning of plants
          • Small piece of tissue taken from plant to be clones, (usually from shoot tip) = an explant
            • Explant placed on a nutrient growth medium
              • Cells in tissue divide but do not differentiate. Instead form mass of undifferentiated cells = a callus
                • After few weeks, single callus cells removed and placed on growing medium containing plant hormones that encourage shoot growth
                  • Further weeks, growing shoots transferred onto different growing medium containing different hormone concentrations that encourage root growth
                    • Growing plants transferred to greenhouse to be acclimatised + grown further before planted outside
      • Advantages of plant cloning in agriculture
        • Propagation using callus culture means:
          • Farmers know what the crop plant produced will be like because it it cloned from plants with known features
            • Farmers' costs are reduced because all crop is ready for harvest at the same time
              • 'Refinement' of selective breeding
        • Micropropagation is much quicker than selective breeding
          • Huge numbers of genetically identical plants can be generated from small number of plants or a single valuable plant
        • Farming methods now more regulated and (although genetically uniform plants still grown) areas given to specfic crops + distance between areas of same crop are controlled
          • Limit effects of arrival of new pathogens
      • Disadvantages of plant cloning in agriculture
        • Selective breeding over generations = reduced genetic variation
          • Farmers identified + grown only crops with useful features
          • Some fruit trees cannot be grown from seed because new tree will have combinstion of genes that not give correct fruit
        • Genetic uniformity means all plants are equally susceptible to any new pest, disease or environmental change
          • 1845-1851, Ireland: Potato famine 1 mill. ppl died from starvation + disease
            • Potato crop lost due to infection by fungus-like protoctist
    • Cloning Animals
      • Artificial cloning - two ways:
        • Splitting embryos
          • 'Artificial identical twins'
          • Cells from developing embryo seperated out, with each one going on to produce seperate (genetically identical) organism
        • Nuclear transfer
          • Using enucleated eggs
          • Differentiated cell from adult taken + nuclus removed
            • Nuclus placed in cell which had own nucleus removed
              • Such a cell = enucleated
          • Dolly the sheep in 1996, 277 attempts
      • Only embryonic cells naturally capable of going through stages of developm. to generate new organism
        • Totipotent stem cells
      • Cloned animal is one that has been produced using the same genetic information as another animal
        • Such an animals has same genotype as donor organism
      • Advantages of cloning animals
        • High-value animals (cows who give high yield milk) can be cloned in large numbers
        • Rare animals can be cloned to preserve the species
        • Genetically modified animals(sheep that produce pharmaceutical chemicals in milk) can be quickly reproduced
      • Disadvantages of cloning animals
        • High-value animals are not necessarily produced with animal welfare in mind
        • As with plants, genetic uniformity in a species makes it unlikely to be able to cope with or adapt to changes in environment
        • Still unclear whether animals cloned using nuclear material of adult cells will remain healthy in the long-term
      • What is non-reproductive cloning?
        • Developments in cloning = possibility of using cloned cells to generate cells, tissues + organs to replace those damaged
        • Advantages of using cloned cells
          • Being genetically identical to indiviv. own cells means will not be rejected because immune system will not recognise as foreign
          • Cloning + cekk culture techniques could mean end to current problems of waiting for donor organs to become available for transplant
          • Cloned cells = totipotent, so can generate any cell type. Damage by some diseases cannot currently be repaired by transplantation
          • Using cloned cells less likely to be dangerous than major operation (e.g. heart transplant)
        • Possibilities for non-reproductive cloning:
          • Regeneration of heart muscle cells following heart attack
          • Repair of nervous tissue destroyed by diseases such as multiple sclerosis
          • Repairing spinal cord of those paralysed by accident (broken neck or back)
    • Clones in Nature
      • Advantages of asexual reproduction
        • Quick, allowing organisms to reproduce rapidly + take advantage of resources in the environment
        • Can be completed if sexual reproduction not possible
        • All offspring have genetic information to enable them to survive in environment
      • Identical twins
        • Zygote splits in two - natural twins
      • Clones = exact copies. Genetic cells or whole organisms that carry identical material because derived from same original DNA
      • Disadvantages of asexual reproduction
        • Does not produce any genetic variety - any genetic parental weakness will be in offspring.
          • If environment changes all genetically identical organisms will be equally susceptible
      • Natural vegetative propagation in plants
        • English Elm
          • Adapted to reproduce asexually following damage to the parent plant
            • Allows species to survive disease or burning
          • New growth (root suckers/basal sprouts) appear within 2 months of destruction of main trunk
            • Suckers grow from meristem tissue in trunk close to ground - where damage least likely to have occured
        • Advantages to the elm of vegetative propagation
          • Root suckers help the elm spread because they grow all around the original trunk
            • When tree stressed or dies, circle of new elms grow = clonal patch
            • This puts out new suckers so that the patch keeps expanding as far as resources permit
        • Disadvantages to the elm of vegetative propagation
          • 20th century, Europe: Dutch elm disease spread (fungal disease carried by beetle)
            • Leaves withered, followed by death of branches and trunks
            • Root suckers grew but died when 10cm diameter -> new suckers clones of original tree, no resistance against fungal attack
          • No genetic variation within cloned population, so natural selection cannot occur
            • Clones just as vulnerable as original tree
  • Clones in Nature
    • Advantages of asexual reproduction
      • Quick, allowing organisms to reproduce rapidly + take advantage of resources in the environment
      • Can be completed if sexual reproduction not possible
      • All offspring have genetic information to enable them to survive in environment
    • Identical twins
      • Zygote splits in two - natural twins
    • Clones = exact copies. Genetic cells or whole organisms that carry identical material because derived from same original DNA
    • Disadvantages of asexual reproduction
      • Does not produce any genetic variety - any genetic parental weakness will be in offspring.
        • If environment changes all genetically identical organisms will be equally susceptible
    • Natural vegetative propagation in plants
      • English Elm
        • Adapted to reproduce asexually following damage to the parent plant
          • Allows species to survive disease or burning
        • New growth (root suckers/basal sprouts) appear within 2 months of destruction of main trunk
          • Suckers grow from meristem tissue in trunk close to ground - where damage least likely to have occured
      • Advantages to the elm of vegetative propagation
        • Root suckers help the elm spread because they grow all around the original trunk
          • When tree stressed or dies, circle of new elms grow = clonal patch
          • This puts out new suckers so that the patch keeps expanding as far as resources permit
      • Disadvantages to the elm of vegetative propagation
        • 20th century, Europe: Dutch elm disease spread (fungal disease carried by beetle)
          • Leaves withered, followed by death of branches and trunks
          • Root suckers grew but died when 10cm diameter -> new suckers clones of original tree, no resistance against fungal attack
        • No genetic variation within cloned population, so natural selection cannot occur
          • Clones just as vulnerable as original tree

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