Chapter 13 – Genetic Engineering

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Chapter 13 Genetic Engineering

• L2 Biology

Has Bonnie been bred by selective breeding?
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Selective Breeding

• Choose organisms with the desired traits and
  breed them, so the next generation also has those
  traits
• Nearly all domesticated animals and crops
• Luther Burbank (1849-1926) developed gt800 diff
  varieties of plants in his lifetime

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Hybridization

• Breed two dissimilar organisms
• In plants often results in better lines
  hybrids are larger, stronger, etc
• In animals hybrids produced may be weaker and
  sterile
• Ex wolf x dog ---- weak wolf-dog
• Ex horse x donkey ---- mule (sterile)

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Lion x Tiger Liger
Horse x Donkey Mule
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Inbreeding

• Breeding two organisms that are
• very similar to produce offspring
• with the desired traits.
• Ex dog breeds

• Risks might bring together two individuals
  that carry bad recessive genes many purebred
  dogs have genetic disorders that mutts dont get.

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Increasing Variation

• Induce mutations the ultimate source of genetic
  variations among a group of organisms
• Mutagens used radiation and chemicals
• Some organisms are formed that have more
  desirable variations.

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Producing new kinds of bacteria

• Can expose millions of bacteria at one time to
  radiation increases chances of producing a
  successful mutant.
• Ex bacteria that can digest oil have been
  produced this way

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Producing new kinds of plants

• Drugs that prevent chromosomal separation in
  meiosis have been used to create plants that have
  more than two sets of chromosomes (2n). These
  are called polyploid plants.
• Ex bananas, citrus fruit, strawberries, many
  ornamental flowers

Diploid corn Tetraploid corn
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Manipulating DNA tools of the molecular
biologist

• DNA extraction open the cells and separate DNA
  from all the other cell parts.
• Remember the kiwi lab?

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• Cutting DNA
• Use restriction enzymes
• each one cuts DNA at a
• specific sequence of nucleotides.
• This will make different
• lengths of DNA

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• Separating DNA Gel Electrophoresis
• Place fragments at one end of a porous gel we
  use agarose gel
• Apply an electric current The DNA is negatively
  charged and will travel toward the positive end
  of the gel.
• The larger pieces of DNA move slower, the smaller
  ones faster.
• Used to compare genomes of different organisms or
  different individuals.
• Also used to locate and identify one particular
  gene out of an individuals genome.

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Click here for animation about gel electrophoresis
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Using the DNA Sequence

• Sequence can be read, studied, and changed.
• Techniques used to study DNA sequences
• Use DNA polymerase and the 4 DNA bases to produce
  a new DNA strand complementary to unknown strand
  some of the bases are dyed.
• Dye-labeled strands are then separated using gel
  electrophoresis and the order of the bands tells
  the DNA sequence of the unknown strand.

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• Cutting and Pasting make recombinant DNA (DNA
  from two different organisms).
• Cut out the gene to be inserted, use same
  restriction enzyme to cut the receiving DNA
  strand, attach the two DNA strands

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Making Copies

• Polymerase Chain Reaction (PCR) is used to make
  many copies of the same piece of DNA like a
  photocopy machine makes copies of papers.
• This is useful if there is only a very small
  sample of DNA available (as that found in a small
  blood drop at a crime scene)

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Cell Transformation

• A cell takes in DNA from outside the cell and
  that DNA then becomes part of the cells DNA.
• Bacteria place DNA in the solution that
  bacteria live in, and some of that DNA will be
  taken in by the bacteria cells.

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Bacteria Transformation using Recombinant DNA

• Cut a gene with a restriction enzyme out of a
  human cell (ex gene for insulin or growth
  hormone work well)
• Cut a bacterial plasmid using the same
  restriction enzyme (DNA ends will be
  complementary)
• Insert Human gene into bacterial plasmid
• Insert plasmid back into bacterial cell
• Bacteria will multiply, and all offspring will
  have that gene these bacteria will then follow
  the directions of the human gene and make the
  protein coded for (insulin or human growth
  hormone)

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Transforming Plant Cells

• Use bacterial plasmid to insert desired gene into
  DNA of a plant

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Transforming Animal Cells

• Directly inject DNA into the nucleus of an egg
  it will become part of the chromosomes.
• Has been used to replace specific genes.

Glowing mouse cells in embryos that were made
from sperm given the gene for bioluminescence
from jellyfish now all the cells glow!
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Applications of Genetic Engineering

• Gene for luciferase was isolated from fireflies
  and inserted into tobacco plants they glowed!
• Transgenic organisms contain genes from other
  species

A transgenic mouse, which carriesa jellyfish
gene, glows green underfluorescent light.  
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Transgenic Organisms

• Bacteria - Make human proteins like insulin
• Plants 52 of soybeans, 25 of corn in US in
  year 2000. Some produce natural insecticide, some
  resist weed-killers, may soon be used to produce
  human antibodies rice with vitamin A.

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• Animals mice with immune systems like humans
  farm animals that grow faster and larger with
  extra copies of growth hormone genes animals
  with leaner meat chickens resistant to bacterial
  infections.

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Cloning

• Clone member of a population
• of genetically identical cells
• produced from a single cell.
• 1996 Dolly cloned
• 1st mammal (sheep) cloned.
• She got arthritis several years
• earlier than most sheep
• Died in 2003

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The End