Genome TeacherLeader

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Genome Teacher-Leader Professional Development
Session Funded by the Pfizer Foundation Presenter
Kathy Frame
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Can Sunscreen Protect DNA?

• Observations?
• Questions?
• Hypothesis?
• Predictions?

• Results?
• Testing?
• Conclusions?

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Experimental Design

• What do you observe?
• What questions come to mind?
• What is your tentative explanation, or
  hypothesis?

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Experiment

• What predictions can you make with your
  hypothesis?
• How can you test your hypothesis?
• Design an experiment?

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Choosing an OrganismYeast Life Cycle
http//www.phys.ksu.edu/gene/

• Yeast Asci. Each ascus contains the four spores
  produced as a result of a single meiosis. Its
  this characteristic of keeping the meiotic
  products together that makes baker's yeast a
  powerful tool in genetics.

http//www.phys.ksu.edu/gene/
Yeast mating mixture showing the characteristic
shapes of yeast cells in this step of the life
cycle.
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Yeast Life Cycle
http//www.phys.ksu.edu/gene/
http//www.phys.ksu.edu/gene/
Yeast Asci. Normally spores form a tetrahedral
shape inside the ascus. Occasionally an ascus
forms that has all four spores in one plane.

• Budding Yeast Cells

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Yeast Colony Growth Beginning the Experiment

• Streaking for Single Cells
• It is possible to use sterile toothpicks to
  streak a sample of cells far enough apart so that
  single cells grow into separate colonies.
• Use this culture to start the experiment.

http//www.phys.ksu.edu/gene/
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Basis ProcedureSetting Up the UV Exposure Plates
Step 4 Dependent Variable Use different
materials to cover the plate, such as sunglasses.
http//www.phys.ksu.edu/gene/
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UV-Yeast Growth DataSunglass Protection

• The plate was exposed to sunlight
• while a portion of the cells were shaded with
  sunglasses.

http//www.phys.ksu.edu/gene/
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Refining the ProcedureTesting the Effects of
Sunscreen

• Step 4
• Dependent Variable
• Divide the plate into sections.
• Apply sunscreen or controls to the sections.

cover
SS
nothing
http//www.phys.ksu.edu/gene/
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UV-Yeast Growth DataThe Effect of Sunscreen
4 min. exposure to sunlight
http//www.phys.ksu.edu/gene/
http//www.phys.ksu.edu/gene/

• The cells on one half of the plate were shaded
  with dark paper. 1/4 were shaded with sunscreen
  and 1/4 were unprotected.

The cells under the paper grew well. The cells
under the sunscreen grew little. The unprotected
cell barely grew at all.
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Test for Allelism
http//www.phys.ksu.edu/gene/
http//www.phys.ksu.edu/gene/

• Can You Explain These Data?

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Conclusions

• This experiment introduces two refinements of the
  gene concept
• Mutants in different genes can have the same
  phenotype
• There can be different forms of the same gene
  (alleles)
• And, more questions!