Ch 13

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Ch 13 Genetic Engineering
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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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GMOs (Genetically modified organisms)
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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 pea lab?

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DNA Extraction

• Chemical treatments cause cells and nuclei to
  burst
• The DNA is inherently sticky, and can be pulled
  out of the mixture
• This is called spooling DNA

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Spooled DNA
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Cutting DNA

• Restriction enzymes cut DNA at specific sequences
• Useful to divide DNA into manageable fragments

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Electrophoresis

• DNA can be separated based on size and charge
• The phosphate groups are negatively charged
• DNA is placed in a gel and electricity is run
  through

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Electrophoresis

• Negative DNA moves toward the positive end
• Smaller fragments move farther and faster

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Electrophoresis
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Click here for animation about gel electrophoresis
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Steps in DNA Sequencing

• Many copies of a single strand of DNA are placed
  in a test tube
• DNA polymerase is added
• A mixture of nucleotides is added some of which
  have dye molecules attached
• Each base (A,T,C,G) has a different color dye

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Steps in DNA Sequencing

• By chance, some dyed nucleotides some regular
  ones are added
• Dye molecules are large and stop the chain from
  growing

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DNA Sequencing

• The result is DNA fragments of multiple sizes
  with colors that can be identified

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DNA Sequencing

• After the gel separates the resulting fragments
  by size, we 'read' the sequence from bottom to
  top.

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Copying DNA

• Polymerase Chain Reaction
• Also called PCR
• A method of making many copies of a piece of DNA

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Steps in Copying DNA

• A DNA molecule is placed in a small test tube
• DNA polymerase that can work at high temps is
  added

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Steps in Copying DNA

• The DNA is heated to separate the two strands
• Primers, short pieces of DNA complementary to the
  ends of the molecule to be copied, are added

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Copying DNA

• The tube is cooled, and DNA polymerase adds new
  bases to the separated strands

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PCR
Large amounts of DNA can be made from a small
starting sample
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Cloning

• Clone- a member of a group of genetically
  identical cells
• May be produced by asexual reproduction (mitosis)

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Cloning organisms

• A body cell from one organism and an egg cell
  from another are fused
• The resulting cell divides like a normal embryo

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Cloning Dolly
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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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Bacterial plasmids in gene cloning
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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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• http//learn.genetics.utah.edu/content/begin/dna/f
  irefly/

Tobacco Plant containing Luciferin gene from
Firefly
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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.