Cloning

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Cloning

• A clone is an exact genetic copy of an individual
• Many organisms have clonal reproduction fission
  (bacteria, protozoa), budding (some plants,
  invertebrates), parthenogenesis (some fish,
  insects, lizards)
• Clonal reproduction of plants, using cuttings or
  other culturing techniques, mastered by humans
  for millennia (e.g. bananas)

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Asexual Organisms
A few species, like this gecko, are
parthenogenic. This means that all individuals
are female, and their offspring are exact genetic
copies of themselves, or clones.
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Asexual Organisms
Most asexual species have close relatives that
are sexual. The whiptail lizard is a
parthenogenic species that formed as a hybrid of
two other species. It tricks males of the other
species to mate with it, because it needs sperm
to activate its eggs
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Cloning

• Vertebrate cloning difficult especially mammals
  birds
• Dolly was 1of 276 attempts
• Current technology
• Harvest the nucleus of a cell from an adult
• Inject it into an egg cell that has had its
  nucleus removed
• Make sure that cells begin to divide normally (an
  embryo begins to form) This is the hard step
• Place the developing embryo in a foster mother

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Cloning

• Cloning (potentially) permits the rapid,
  economical reproduction of individuals with
  desirable traits
• With serial cloning, genetic lines can be
  preserved (almost) exactly
• Serial cloning may destabilize chromosomes
• Mutations will accumulate a cost of clonal
  reproduction
• Even though the nucleus of the egg is removed,
  some of the egg-donors genes remain, in the
  mitochondria thus the first generation is not a
  perfect clone
• Long term risk in terms of lost genetic diversity
• More vulnerable to disease epidemics
• Less variation to adapt to environmental change

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Gene Therapies

• Introduce substances that halt the activity of
  certain genes (AZT)
• Introduce substances that (over) promote activity
  of certain genes (gamma globin)
• Introduce new, functional genes true Gene Therapy
• Experimental, currently tested primarily on
  critically ill patients

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Gene Therapy

• Vehicle or Vector
• e.g. weakened virus
• Recipient cells
• cultured cells or in vivo somatic cells e.g bone
  marrow
• The introduced sequence
• Marker (so you know it worked)
• Promoter (to cause transcription)
• The Gene

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The Problems

• Must immuno-suppress the patient
• Efficiency of transfer often low
• Duration of expression often short
• Unknown risks permanent unwanted changes
  (mutations) to somatic (or germ cells), viral
  infections, cancer or other diseases associated
  with breakdown in genetic regulation?

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Genetically Modified (Transgenic) Crops

• 50 of soybeans, 25 of corn grown in the US are
  transgenic (have a gene from another species
  added via biotech)
• Main transgenic traits herbicide tolerance, Bt
  toxins to kill insect pests, virus resistance
• Future transgenic traits vitamins, vaccines
  (inactivated viruses)
• Potential to reduce uses of agrochemicals,
  increase food production, improve quality of
  plant products (including novel ones)

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Genetically Modified (Transgenic) Crops

• Using specialized enzymes, chop up gene
  sequences, select and connect desirable sequences
  to form a cassette
• Sequence must include a marker, promoter,
  transgene
• Flanked by sticky ends
• Infect a bacteria (E. coli) to produce quantities
  of cassettes via bacterial clonal reproduction
• Purify sequences, inject sequences into cells
• Gene gun
• Infective bacteria
• Select plant cells with the marker
• Propagate selected plants clonally
• Produce new plants clonally or through sexual
  crosses

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Problems with Transgenic Crops

• Doesnt work very well - yet
• Risk of traits spreading to weeds, producing
  super weeds, or pests developing resistance to
  transgenic defenses
• Risk to non-target organisms
• No unusual health risks (?), requires strict
  testing
• Reduced genetic diversity puts crops at (long
  term) risk
• Agricultural resources become monopolized by a
  small number of gigantic agrobusinesses

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Transgenic Animals

• Potentially quite useful
• Animal models of human diseases by introducing
  human genes
• Targeted production of pharmaceutical proteins
  (human enzymes, hormones, growth factors)
• Modification of animal anatomy physiology

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Transgenic Animals

• Create cassette enhancer promoter gene
  plus sticky ends
• Enhancer often designed to restrict activation of
  the gene to a targeted tissue (e.g liver) only
• Infect a bacteria (E. coli) to amplify the
  cassettes via bacterial clonal reproduction
• Collect and purify the cassettes, test for
  activation in eukaryotic cells
• Inject cassettes into a newly fertilized egg
  cells
• Transfer embryos into a surrogate mother
• Analyze babies, breed or reproduce clones of
  those that express the transgene and have the
  fewest other problems

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Problems with Transgenic Animals

• Doesnt work very well yet
• Cassettes integrate randomly into genome,
  sometimes knocking out genes
• Sometimes multiple copies integrate
• Integration not always stable
• Same worries as transgenic crops
• Animal welfare