Studying Biology:

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Studying Biology

• Start with a question.
• For example
• How? Why? When? Where? Etc?
• How do we get answers?
• Strong Inference presents one method

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The Rules of Strong Inference Strong Inference
is a method for looking at scientific problems by
trying to disprove hypotheses and accepting the
hypotheses that can not be disproved. Using
Strong Inference entails following these rules
(from an article by John Platt, 1964) 1.
Devise multiple hypotheses. 2. Design
experiment(s) to eliminate one or more of the
hypotheses. 3. Carry out the experiments in a
manner that gives a clean result. 4. Repeat.
Refine hypotheses.
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Signal Transduction
External
Stimulus
Internal
Effector
Effector
Effector
Effector
Response
Perception (by receptor)
Stimulus
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Changes in Ca2 levels within the cytoplasm is a
common signal in eukaryotic cells.
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During signal transduction, calcium can be
released into the cytoplasm
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General model of Ca2 signaling
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Cytosolic Ca2 concentrations in plant tissues
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Stimulus induced cytosolic changes in calcium
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Calcium-regulated physiological processes in
plants
Membrane structure and function Secretion Growth
hormone action Asymmetric growth Polarized
growth Spore germination
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Arabidopsis Model System for Dissecting Gene
Function in Higher Plants

• Genome completely sequenced
• Short life span - easy genetic analysis
• T-DNA insertional mutant libraries available

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Arabidopsis Annexins

• Eight different members in the gene family
• Range from 30 to 80 identity
• Localized in secretory cell types
• Plasma membrane associated

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Model for annexin functions in plants