6.2.1 Cloning

• Cloning - definition


  Producing genetically identical cells or organisms from the cell of an existing organism
• Vegetative Propagation - definition


  Production of plant clones from non-reproductive tissues
• Horticulture - definition


  Branch of agriculture that deals with plants
• Agriculture - definition


  Cultivation and breeding of plants, animals and fungi for food or other resources
• Therapeutic cloning - definition


  Use of cloned cells, tissues or organs for the treatment of individuals in order to replace those damaged
• Taking cuttings - definition

  Removing and planting short sections of a stem to produce clones
• Micropropagation - definition


  When tissue culture is used on mass to quickly produce clones - used extensively in horticulture and agriculture
• Tissue culture - definition


  The method of growing plant cells, in isolation from the parent plant under sterile conditions in/on a nutrient culture medium of known composition.
• Rhizomes

  • stem structures
  • grow HORIZONTALLY UNDERGROUND, away from the parent plant
  • have 'nodes' where new roots and shoots develop
  • e.g. bamboo
• Stolons (runners)

  • HORIZONTAL, ABOVE GROUND stems
  • new shoots and roots develop at nodes or form at ends of stolon
  • e.g. strawberries
• Suckers

  • shoots grow UP from HORIZONTAL UNDERGROUND roots
  • e.g. elm trees
• Tubers

  • large underground structures
  • act as a FOOD STORE
  • swollen underground stems
  • covered in 'eyes' that can sprout to form a new plant
  • e.g. potatoes
• Bulbs

  • UNDERGROUND FOOD STORE
  • swollen and tightly packed
  • new bulbs can develop from the original one to form new original plants
  • e.g. onions
• Rooting powder

  Contain hormones that induce root formation
• Cutting tips:

  • use non-flowering stems
  • make an oblique cut in the stem (increases surface area)
  • reduce number of leaves (transpiration rate)
  • keep well watered (as it has no roots)
• Cuttings - method

  1. take a cutting using a scalpel between 5-10cm, from the stem
  2. REMOVE LEAVES from cutting
  3. dip lower end in ROOTING POWDER
  4. plant cutting into a pot containing a suitable growth medium (e.g. well drained compost)
  5. ensure a WARM and MOIST environment - plastic bag or propagator)
  6. plant elsewhere once strong enough and has formed its own roots
• Tissue Culture - method

  1. cells are taken from original plant (from the stem and root tip - stem cells that can develop into any type of cell)
  2. sterilisation (e.g. bleach)- kill microorganisms - bacteria and fungi compete for nutrients with the plant cell
  3. placed on a culture medium - containing plant nutrients (glucose) and growth hormones (auxin)
  4. cells will divide and grow into a small plant, then planted in soil
• FOR TISSUE CULTURE

  • clones are genetically identical - desired characteristics are preserved
  • controlled environment - can be reproduced any season
  • require less space
  • can mass produce quickly
  • can clone endangered and rare plants or those that don't readily produce
  • can grow whole plants from genetically engineered plants
• AGAINST TISSUE CULTURE

  • clones are genetically identical - undesirable characteristics remain, no genetic variation so susceptible to the same diseases, could kill off entire population
  • high energy requirements, high skill requirements - high production costs
  • not suitable on a small scale
  • contamination by microorganisms result in a complete loss of plants
• Animal clones occurring naturally

  • after an egg is fertilised
  • may split in early stages of development
  • develops into multiple embryos with same genetic information
• Uses of animal cloning:

  • research - e.g. testing new drugs, variables from genetic differences are removed
  • saving endangered animals
  • agriculture - increase number of animals with desired characteristics to breed from
  • to produce useful substances from animals
  • cloning embryonic stem cells to replace damaged tissues e.g. heart disease, spinal chord injuries, Parkinson's disease - if made from patients own cells, won't be rejected by immune system
• ARTIFICIAL EMBRYO TWINNING

  1. egg cell is extracted and fertilised in a petri dish
  2. it divides at least once, forming an embryo in vitro (outside a living organism)
  3. individual cells from the embryo are separated into separate Petri dishes to develop into an embryo each
  4. embryos implanted into surrogate cows who have been prepared with hormones
  5. embryos develop - offspring are identical
• SOMATIC CELL

  Any cell that isn't a reproductive cell
• SCNT

  Somatic Cell Nuclear Transfer
• SCNT

  1. a somatic cell is taken from A, the nucleus is extracted and kept
  2. an oocyte (immature egg cell) is taken from B, the nucleus is removed to form an enucleated oocyte
  3. the nucleus from A is inserted into the enucleated oocyte from B
  4. they are fused together and stimulated to divide (by electrofusion - electrical current), producing an embryo
  5. embryo is implanted into a surrogate mother, prepared with hormones, it is left to develo
• FOR ANIMAL CLONING

  • desirable characteristics are always passed onto clones
  • infertile animals can be reproduced
  • endangered species -> biodiversity
  • development of new diseases
  • can clone whenever needed
• AGAINST ANIMAL CLONING

  • difficult, time consuming, expensive
  • no genetic variety - undesirable characteristics are passed on, susceptible to same diseases - one could wipe them all out
  • clones may not live long - unethical
  • use of embryos for a stem cell source is viewed as killing a life