Molecular Genetics and Genetic Engineering

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Molecular GeneticsandGenetic Engineering

• Mrs. Volins Biology

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Selective Breeding

• Has been practiced for 1000s of years
• Allows only certain individuals with desired
  characteristics to reproduce
• Dog breeds
• Domestic animals
• Hybrid plants

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• Luther Burbank
• American botanist
• Practiced selective breeding with hundreds of
  varieties of plants
• Developed Burbank potato in response to the
  potato blight in Ireland

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Hybridization

• Crossing dissimilar individuals to bring together
  best traits of the parent organisms

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Increasing Genetic Variation

• Inducing mutations
• chemicals
• radiation
• Bacteria
• Oil spill cleanup
• Plants
• Polyploid plants(many sets of chromosomes)-- -
  Larger and stronger
• - Crop plants bananas, citrus

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• What would happen if a segment of DNA was removed
  from one organism and inserted into the DNA of a
  completely different species?

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Genetic Code is universal

• The genetic code is same for every organism---
• Example
• GUC codes for valine in bacteria
  
  in grass
  in sparrows
• in humans
• Because the genetic code is universal, segments
  of DNA can be transferred to other organisms to
  produce desired proteins
• 
  

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Manipulating DNA

• Genetic engineering - process of making changes
  in DNA code of living organisms
• Ability to swap genes from one organism to another

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Herbert Boyer and Stanley Cohen 1972

• Created the first
• genetically engineered organism
• Spliced a piece of toad DNA into a bacterium
• When the bacterium reproduced, it copied the
  foreign DNA into its offspring, acting as a
  natural factory producing the toad protein.

Herbert Boyer
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Genetic Engineering

• A quick and easy way to produce proteins such as
  human growth hormone and insulin

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• How can a bacterial cell produce human insulin?

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Splicing a human DNA segment into a bacterium 1.
An enzyme cuts (cleaves) a DNA sequence from
human cell 2. The same enzyme is used to cut
open (cleave) a piece of circular bacterial DNA
called a plasmid 3. These enzymes are called
restriction enzymes 4. Different restriction
enzymes recognize different sequences of bases
and cut the DNA at specific points 5.
Restriction enzymes are like molecular
scissors
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Restriction enzyme EcoRI cuts between G and A in
sequence GAATTC
(See page 322)
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Restriction enzymes the
molecular scissors
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sticky ends
sticky ends
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6. The human gene is inserted into the plasmid.
DNA ligase joins together the sticky ends. 7.
This process of a cell incorporating DNA from the
outside is called transformation 8. The DNA is
referred to as recombinant DNA (from more than
one organism) 9. The bacterial DNA now
transcribes the code for the human protein.
10. In this example, bacteria will produce large
quantities of human insulin.
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Genetic Engineering Example---Insulin
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Genetic Engineering Examples
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Applications of Genetic Engineering

• Transgenic organisms--
• Organisms that contain genes from other
  organisms

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Transgenic organisms

• Transgenic bacteria now produce insulin, growth
  hormone, and clotting factor
• Transgenic livestock
• Grow faster
• Less fatty
• Resistant to infection
• Transgenic plants
• Gene that makes a plant resistant to insects
• Gene that makes a plant resistant to weed killers

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Golden Rice is genetically engineered

• Two genes have been inserted through genetic
  engineering to cause plant to produce
  beta-carotene (provitamin A).
• 1-3 million deaths/year result from vitamin A
  deficiency.
• 500.000 children go blind each year due to
  vitamin A deficiency.

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Roundup Ready crops are genetically engineered

• Not affected by herbicide Roundup (glyphosate)
  used to kill weeds in fields
• Soybeans, cotton, corn, canola, and more

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Boll weevil on a cotton boll
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Transgenic Cotton
Left Insect-infested cotton boll Right Cotton
boll from plant that has the insect resistance
Bt gene (from Bacillus
thuringiensis)
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Transgenic tobacco plant bearing the luciferase
gene from a firefly
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Controversy over Genetically Modified Organisms
(GMOs)

• Unresolved questions
• Genes spread to unintended targets creation of
  superweeds
• Allergic effects
• Antibiotic resistance
• Many unknowns
• Greenpeace objects to all GMOs

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Cloning
Dolly

To produce a genetically identical copy of an
organism Dolly the Sheep---first clone of an
adult mammal (Ian Wilmut, 1997, Scotland)
Dollys first lamb
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• Other animals that have been cloned
• Goat, mouse, pig, cat, rabbit
• Cloning has not been successful with
• Monkey, chicken, horse

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• In 2005 The first dog was
  cloned in South Korea
• Snuppy was made from a cell taken from the ear of
  a three-year-old male Afghan hound.

Snuppy, the puppy cloned at Seoul National
University
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• Practical uses of cloning
• Produce substances which have medical or
  scientific value
• Save endangered species
• other
• Ethical concerns over cloning
• Attempts to clone humans
• other

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What ever happened to Dolly?

• In 1998 Dolly gave birth to Bonnie.
• Later offspring were Sally and Rosy,
• then Lucy, Darcy, and Cotton

Bonnie
At age 5, she developed arthritis treated with
anti-inflammatory drugs
FDA says meat from cloned animals and their
offspring is safe to eat. Such meat is not on
the market though
In 2003, at age 6, Dolly was euthanized due to
progressive lung disease. (Normal life
expectancy is 11 or 12.) Vets think this was
unrelated to her being a clone because other
sheep in the flock died of the same disease
Ian Wilmut is against human cloning
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Gene Therapy
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• Gene therapy - replacement of an absent or
  faulty gene with a normal gene
• Currently a high risk, experimental procedure

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