Genetic Engineering

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Genetic Engineering

• Georgia Performance Standards
• Examine the use of DNA technology in
• forensics, medicine, and agriculture

• Essential Questions
• Should there be limits on how DNA technology is
  used?
• How is DNA technology applied to solving
  problems?

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Student Outcomes

• How DNA comparison is used in forensic science
• The process of genetic engineering through the
  use of recombinant DNA
• Examine and question complex bioethical issues
  involving the use of DNA technology in modern
  medicine, industry, agriculture and forensics

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Warm-up

• A New Breed
• The tomatoes in your salad and the dog in your
  backyard are a result of selective breeding.
• Over thousands of years, humans have developed
  breeds of animals and plants that have desirable
  characteristics.
• How do breeders predict the results of crossing
  individuals with different traits?

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Warm-up

• Think of two very different breeds of dogs that
  are familiar to you. On a sheet of paper,
  construct a table that has the following three
  heads the name of each of the two dog breeds,
  and Cross-Breed.
• 2. The rows of the table should be labeled with
  characteristics found in both breeds of dogs.
  Examples might include size, color, type of coat,
  intelligence, aggression, and so on.
• 3. Fill in the column for each of the two dog
  breeds. In the column labeled Cross-Breed,
  write in the characteristic you would expect to
  see in a cross between the two breeds you have
  selected.

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Selective Breeding

• Selective Breeding- a method of improving a
  species by allowing only those individual
  organisms with desired characteristics to produce
  the next generation
• Hybridization
• Inbreeding

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Hybridization

• Hybridization is a breeding technique that
  involves crossing different individuals to bring
  together the best traits of both organisms
• Ex combining the disease resistance of one plant
  with the food-producing capacity of another
  produces a hardier plant that increased food
  supply.

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Inbreeding 

• Inbreeding is the continued breeding of
  individuals with similar characteristics.
• Used to maintain desired characteristics
• Inbreeding helps to ensure that the
  characteristics that make each breed unique will
  be preserved.
• Risks Most of the members of a breed are
  genetically similar and genetic defects can
  arise.

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Concept Map
Selective Breeding
consists of
Inbreeding
Hybridization
which crosses
which crosses
Similar Organisms
Dissimilar Organisms
for example
for example
which
which
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Increasing Variation

• Sometimes breeders want more variation than
  exists in nature.    
• Breeders can increase the genetic variation in a
  population by inducing mutations, which are the
  ultimate source of genetic variability.
• Radiation
• Chemicals

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Plant Breeding

•  Drugs used in plant breeding sometimes cause
  plants to produce cells that have double or
  triple the normal number of chromosomes.
• Plants grown from such cells are called polyploid
  because they have many sets of chromosomes.
• Polyploidy produces larger and stronger plants,
  which increase the food supply for humans.

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Checkpoint Questions

• Give one example of selective breeding.
• Relate genetic variation and mutations to each
  other.
• 3. How might a breeder induce mutations?
• 4. What is polyploidy?
• 5. Suggest ways that plants could be altered to
  improve the worlds food supply.

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Manipulating DNA

• How are changes made to DNA?  
• Scientists use their knowledge of the structure
  of DNA and its chemical properties to study and
  change DNA molecules.
• Different techniques are used
• to extract DNA from cells
• to cut DNA into smaller pieces
• to identify the sequence of bases in a DNA
  molecule
• to make unlimited copies of DNA.

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Genetic engineering

• Genetic Engineering - making changes in the DNA
  code of a living organism.
• Process
• DNA extraction
• Cutting DNA
• Separating DNA
• Reading the sequence
• Cutting and pasting
• Making copies

Molecular Biology
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DNA Extraction

• How do biologists get DNA out of a cell?
• DNA can be extracted from most cells by a simple
  chemical procedure
• The cells are opened and the DNA is separated
  from the other cell parts.

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Cutting DNA

•  DNA molecules from most organisms are much too
  large to be analyzed, so biologists cut them
  precisely into smaller fragments using
  restriction enzymes.
• Restriction enzymes cut DNA at a specific
  sequence of nucleotides.
• Very precise

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Restriction Enzymes

• This drawing shows how restriction enzymes are
  used to edit DNA.
• The restriction enzyme EcoRI, for example, finds
  the sequence CTTAAG on DNA.
• Then, the enzyme cuts the molecule at each
  occurrence of CTTAAG.
• Different restriction enzymes recognize and cut
  different sequences of nucleotides on DNA
  molecules.

VIDEO
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Separating DNA 

• In gel electrophoresis, a mixture of DNA
  fragments is placed at one end of a porous gel,
  and an electric voltage is applied to the gel.
• When the power is turned on, DNA molecules, which
  are negatively charged, move toward the positive
  end of the gel.
• The smaller the DNA fragment, the faster it
  moves.

• Uses
• Comparing genomes of different organisms or
  individuals.
• Locating and identifying one particular gene out
  of the millions of genes in an individuals
  genome.

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Gel Electrophoresis
Power source
DNA plus restriction enzyme
Longer fragments
Shorter fragments
Mixture of DNA fragments
Gel
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Using the Sequence of DNA

• Reading a DNA sequence is now an automated
  process.
• The pattern of colored bands (Fluorescently
  labeled nucleotides) tells the exact sequence of
  bases in the DNA.
• Each color corresponds to a specific nucleotide
  base (A, G, C, and T)

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DNA Sequencing
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Cutting and Pasting 

• Enzymes make it possible to take a gene from one
  organism and attach it to the DNA of another
  organism.
• Such DNA molecules are sometimes called
  recombinant DNA because they are produced by
  combining DNA from different sources.

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Making Copies

• PCR Process
• 1. DNA is heated to separate strands
• 2. DNA is cooled to allow primers to bind
• 3. DNA polymerase copies the strands

• In order to study genes, biologists often need to
  make many copies of a particular gene.
• A technique known as polymerase chain reaction
  (PCR) allows biologists to make copies of DNA.

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PCR Polymerase Chain Reaction
VIDEO
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Checkpoint Questions

• Describe the process scientists use to manipulate
  DNA.
• 2. Why might a scientist want to know the
  sequence of a DNA molecule?
• 3. How does gel electrophoresis work?
• 4. Which technique can be used to make multiple
  copies of a gene? What are the basic steps in
  this procedure?
• 5. How is genetic engineering like computer
  programming?

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Cell Transformation

• During Cell Transformation, a cell takes in DNA
  from outside the cell.
• Plant and animal
• This external DNA becomes a part of the cells
  DNA.
• One way to make recombinant DNA is to insert a
  human gene into bacterial DNA.
• The new combination of genes is then returned to
  a bacterial cell, and the bacteria can produce
  the human protein.
• video

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Transforming Bacteria

• Recombinant DNA is used.
• The foreign DNA is first joined to a small,
  circular DNA molecule known as a plasmid.
• Plasmids have a DNA sequence that serves as a
  bacterial origin of replication.
• Plasmids have a genetic markera gene that makes
  it possible to distinguish bacteria that carry
  the plasmid from those that dont.

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Transforming Bacteria
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Plant Cell Transformation

• Recombinant plasmids can be used to infect plant
  cells.
• DNA can also be injected directly into some plant
  cells.
• Cells transformed by either procedure can be
  cultured to produce adult plants.    

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Plant Cell Transformation
Agrobacterium tumefaciens
Gene to be transferred
Cellular DNA
Inside plant cell, Agrobacterium inserts part of
its DNA into host cell chromosome
Recombinant plasmid
Plant cell colonies
Transformed bacteria introduce plasmids into
plant cells
Complete plant is generated from transformed cell
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Animal Cell TransformationKnockout Genes

• Recombinant DNA can replace a gene in an animals
  genome.
• The ends of the recombinant DNA recombine with
  sequences in the host cell DNA.
• When the recombinant DNA is inserted into the
  target location, the host cells original gene is
  lost or knocked out of its place.

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Knockout Genes
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Checkpoint Questions

• What is transformation?
• How can you tell if a transformation experiment
  has been successful?
• 3. How are genetic markers related to
  transformation?
• 4. What are two features that make plasmids
  useful for transforming cells?
• 5. Compare the transformation of a prokaryotic
  cell with the transformation of a eukaryotic
  cell.

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Applications of Genetic Engineering

• Scientists have developed many transgenic
  organisms, which are organisms that contain genes
  from other organisms.
• scientists have removed a gene for green
  fluorescent protein from a jellyfish and tried to
  insert it into a monkey.

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Applications of Genetic Engineering

• Transgenic animals are often used in research.
• What might be the benefit to medical research of
  a mouse whose immune system is genetically
  altered to mimic some aspect of the human immune
  system?
• Transgenic plants and animals may have increased
  value as food sources.
• What might happen to native species if transgenic
  animals or plants were released into the wild?

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Transgenic Organisms

• The universal nature of genetic mechanisms makes
  it possible to construct organisms that are
  transgenic, meaning that they contain genes from
  other organisms.
• A gene from one organism can be inserted into
  cells from another organism.
• These transformed cells can then be used to grow
  new organisms.

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Transgenic Bacteria or Yeast

• Transgenic bacteria reproduce rapidly and are
  easy to grow.
• Therefore they now produce a host of important
  substances useful for health and industry.
• human insulin, growth hormone, and clotting
  factor

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Transgenic Animals

• Transgenic animals have been used to study genes
  and to improve the food supply
• Strains of mice
• produced with human genes that make their immune
  systems act similarly to those of humans.
• study the effects of diseases on the human immune
  system.
• Transgenic livestock
• produced with extra copies of growth hormone
  genes.
• such animals grow faster and produce meat that is
  less fatty than that from ordinary animals.
• Transgenic chickens
• resistant to the bacterial infections that
  sometimes cause food poisoning.

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Transgenic Plants

• Transgenic plants help to increase our food
  supply.
• Genes produce a natural insecticide (this avoids
  synthetic pesticide use).
• Genes that enable them to resist weed-killing
  chemicals (allows farmers to grow more food by
  controlling weeds.

• Human antibodies that can be used to fight
  disease
• Plastics that can now be produced only from
  petroleum
• Foods that are resistant to rot and spoilage.

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Cloning

• A clone is a member of a population of
  genetically identical cells produced from a
  single cell.
• Cloned colonies of bacteria and other
  microorganisms are easy to grow, but this is not
  always true of multicellular organisms,
  especially animals.

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Cloning

• Clones are used for medical and scientific value,
  but also causes ethical issues.
• In 1997, Scottish scientist Ian Wilmut stunned
  biologists by announcing that he had cloned a
  sheep

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Cloning
A body cell is taken from a donor animal.
An egg cell is taken from a donor animal.
The nucleus is removed from the egg.
The body cell and egg are fused by electric shock.
The fused cell begins dividing, becoming an
embryo.
The embryo is implanted into the uterus of a
foster mother.
The embryo develops into a cloned animal.
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Cloning of the First Mammal
Section 13-4
A donor cell is taken from a sheeps udder.
Donor Nucleus
These two cells are fused using an electric shock.
Fused Cell
Egg Cell
The nucleus of the egg cell is removed.
An egg cell is taken from an adult female sheep.
The fused cell begins dividing normally.
Embryo
Cloned Lamb
The embryo is placed in the uterus of a foster
mother.
The embryo develops normally into a lambDolly
Foster Mother
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Checkpoint Questions

• 1. List one practical application for each of the
  following transgenic bacteria, transgenic
  animals, transgenic plants.
• 2. What is a transgenic organism?
• 3. What basic steps were followed to produce
  Dolly?
• 4. List reasons you would or would not be
  concerned about eating genetically modified food.

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Warm-up

• As you become more aware of scientific advances
  in genetics, you might realize that with the
  ability to manipulate genes, there comes
  responsibility.
• This ability provides an opportunity to improve
  the lives of many people.
• But there is also a potential for errors or
  intentional misuse of the technology.

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Warm-up

• Working with a partner, answer the following
  questions.
• 1. In what type of situation do you think genetic
  engineeringchanging the genes of organismsis
  warranted? Explain your reasoning about your
  position. If you do not think that genetic
  engineering is ever warranted, explain your
  reasons for your position.
• 2. In what type of situation do you think genetic
  engineering might be misused? Suggest limits that
  might be placed on the manipulation of genes to
  avoid its misuse.

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DNA fingerprinting

• Analysis of sections of DNA that have little or
  no known function, but vary widely from one
  individual to another, in order to identify
  individuals
• The reliability of DNA evidence has helped
  convict criminals as well as overturn many
  convictions.

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Figure 14-18 DNA Fingerprinting
Section 14-3
Restriction enzyme
Chromosomes contain large amounts of DNA called
repeats that do not code for proteins. This DNA
varies from person to person. Here, one sample
has 12 repeats between genes A and B, while the
second sample has 9 repeats.
Restriction enzymes are used to cut the DNA into
fragments containing genes and repeats. Note that
the repeat fragments from these two samples are
of different lengths.
The DNA fragments are separated according to size
using gel electrophoresis. The fragments
containing repeats are then labeled using
radioactive probes. This produces a series of
bandsthe DNA fingerprint.
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The Human Genome Project

• The Human Genome Project is an attempt to
  sequence all human DNA.
• VIDEO

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Gene Therapy

• Curing genetic disorders by gene therapy.
• Gene therapy is the process of changing the gene
  that causes a genetic disorder.    
• In gene therapy, an absent or faulty gene is
  replaced by a normal, working gene.
• This way, the body can make the correct protein
  or enzyme it needs, which eliminates the cause of
  the disorder.

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Figure 14-21 Gene Therapy
Section 14-3
Bone marrow cell
Nucleus
Normal hemoglobin gene
Chromosomes
Bone marrow
Genetically engineered virus
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Think About It

• What will happen to the human species if we gain
  the opportunity to design our bodies

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Checkpoint Questions

• What is the Human Genome Project?
•  Describe how gene therapy works.
• 3. Name two common uses for DNA testing.
• 4. Describe how molecular biologists identify
  genes in sequences of DNA.
• 5. Do you think it should be legal for people to
  use genetic engineering to affect their
  childrens characteristics? Give reasons for your
  answer.