Trailblazers: Investigating Chemotaxis with C.elegans
17. COOL both plates to 4 °C by placing in fridge for 15 minutes. This will further slow worms and help with counting. 18. COUNT the final number of worms in the experimental and control areas. Also count the worms in the middle section of the plate. Worms can be counted under the microscope. Alter- natively the location of each worm on the plate can be marked with a permanent marker under the microscope and the dots counted by eye at a later point. Module III: Collection of C.elegans and Chemotaxis Assay Excerpts from Edvo-Kit #852
Number of wild-type worms near experimental compound: _______ Number of wild-type worms near control: _______ Number of wild-type worms in middle section: _______ Number of mutant strain worms near experimental compound: _______
Number of mutant strain worms near control: _______ Number of mutant strain worms in middle section: _______ 19. CALCULATE a chemotaxis index (CI) for each plate:
CI= (# of worms in experimental area – # of worms in control area) (# of worms in experimental area + # of worms in control area + # of worms in middle section)
CI Index for Wild Type worms: ______
CI Index for Mutant Strain worms: _______
NOTE: A chemotaxis index close to 1 indicates that the chemical is a strong attractant while a chemotaxis index close to -1 indicates that it is a strong repellent. 20. (Optional) SHARE your group’s results from steps 18 and 19 with the class in order to generate a classroom data set of C. elegans responses to multiple chemicals.
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Figure 6: Petri Template
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