Genetic Engineering: How and why scientists manipulate DNA in living cells

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Genetic EngineeringHow and why scientists
manipulate DNA in living cells
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Karyotype

• chart of chromosome
• pairs used to identify
• unusual s of chromosomes
• Down syndrome (Trisomy 21) 3 chrom. at pair
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• Turners syndrome only one X sterile female
  XO
• Klinefelters syndrome extra X
  (maleXXY-sterile)

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Karyotype
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• Nondisjunction causes these unusual s of
  chromosomes chromosomes fail to separate during
  meiosis

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Selective breeding

• We choose desired
• traits breed plants and
• animals to have these traits
• Takes decades
• Examples popcorn,
• dog breeds, cows produce
• 3x more milk than 50 years ago, bigger peaches,
  apple varieties

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Selective breeding 2 methods

• 1. Hybridization cross dissimilar individuals
  to bring together best traits
• Ex. Crossing disease-resistant apple with high
  yield apple apple tree that
• produces a lot and requires
• less pesticides

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• 2. Inbreeding done to maintain traits
• because genetics are so close, often allows
  expression of recessive allele
• Study revealed that
• 20,000 boxers genetically
• look like 70
• -deaf dalmations
• white boxers, heart disease,
• hip dysplasia

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Test cross

• A way of determining genotype
• Cross a known individual -
• (homozygous recessive) with an unknown
  homozygous dominant or heterozygous
• If unknown is homozygous dominant, all offspring
  will show dominant trait
• If unknown is heterozygous, some will show
  dominant trait, some show recessive trait
• Complete Problem Solving Lab 13.1 p.339

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Manipulating DNA
Process How
Cut DNA Restriction Enzymes (like scissors)
Sort DNA Gel Electrophoresis
Analyze DNA DNA fingerprint
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1. Cut DNA Restriction enzymes

• DNA is too large to be analyzed
• Highly specific restriction enzymes from bacteria
  cut DNA into precise pieces between certain base
  pairs
• Ex. EcoRI can only recognize GAATTC it cuts
  between the G and A
• Leaves sticky ends single-stranded overhangs
  used to bond stick to another DNA stand cut
  with the same restriction enzyme
• Practice p.343

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Restriction enzymes
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2. Sort DNA Gel Electrophoresis
3. Result DNA fingerprint
1.Insert restriction-enzyme-cut DNA into gel
2. Add electricity. Shorter fragments move farther
p. 346
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3. Analyze DNA DNA fingerprinting

• Sample from
• blood, hair, skin,
• semen
• Use PCR
• (polymerase
• chain reaction)
• to make more

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Can you match the evidence with the suspect?
PS lab 13.3 p.353
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Human Genome Project (1990-2003)

• Sequenced all 3 billion base pairs of human DNA
  and identified
• all human genes.
• Used to determine
• carriers for diseases
• develop gene
• therapy

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• Product of
• Human Genome
• chromosome
• maps

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• Genetic engineering
• faster than selective
• breeding. Cut DNA
• from one organism,
• insert into another.
• Recombinant
• DNA combining
• DNA from different
• sources

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Transgenic organisms

• Contain genes from other species
• Insert recombinant DNA into a new host
• Use plasmid circle of DNA in bacteria
• Insert recombinant DNA into plasmid, reinsert
  plasmid into bacteria- bacteria clones DNA as it
  divides (mitosis) get lots of copies of DNA
• Used to produce insulin to treat diabetes, human
  growth hormone, blood-clotting factors for
  hemophiliacs, potentially even cancer-fighting
  molecules (interleukin-2 and interferon)

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Recombinant bacteria manufacture insulin
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Cloning

• Uses a single somatic cell from an adult organism
  to grow an entirely new genetically identical
  organism

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Uses of transgenic animals

• Insert spider genes into cells of lactating goats
  manufacture silk along with milk light,
  tough, flexible material ? military uniforms,
  medical sutures
• 30 of US milk produced
• by genetically modified (GM)
• cows
• Pigs GM to produce
• high levels of lean meat

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Transgenic plants Golden Rice GM to have high
levels of beta-carotene essential for health,
eye sight
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Gene therapy

• Absent or faulty genes replaced by normal working
  genes allows body to make proteins or enzymes
  needed, eliminating disorder
• Used to treat SCID (severe combined
  immunodeficiency syndrome)
• Trials for sickle-cell, cystic fibrosis, and
  hemophilia treatments are going on now

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Future possibilities?
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Implications? Ethical issues?

• Patenting life
• Genetic ownership
• GINA (Genetic Information Nondiscrimination Act)
  passed in 2008
• Protects Americans against discrimination from
  employers or insurance companies based on genetic
  information

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