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Mechanisms of Mitosis

Mechanisms of Mitosis

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Mechanisms of Mitosis

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  1. Mechanisms of Mitosis Data Collection

  2. Data Collection Today your team will collect data from • untreated control onions • incubatedtreatmentonions You will repeat data collection again in next week’s lab session.

  3. Treatment vs. Control On each of your two data collection sessions, your team will perform cell counts on • 4 control root tips • 4 treatment root tips (Each team member will do one squash of each.)

  4. Treatment vs. Control Next week, you will be doing more data collection. By the end of next week’s session, each team will have collected a total of • 8 control root tip replicates • 8 treatment root replicates

  5. Data Collection • By now you should be able to recognize root tip cells in the different stages of mitosis. • Root tips vary in size and quality • Count cells in areas where they are clear and not layered.

  6. Data Collection You should count cells in FOUR different fields of view for each root tip. For each field of view, record • Total number of cells • Number of cells in each stage of mitosis

  7. Data Collection AVOID PSEUDOREPLICATION. Do not take more than one root from the same onion. Do not count multiple fields of view from the same root tip as separate samples. All cells counted from an indivdual onion count as one sample/replicate.

  8. Data Collection Your lab instructor will provide you with an entire root from a particular onion labeled with an identification code (e.g., C1, T5, etc.) With a lab marker, write the onion’s ID code on the microscope slide you use for its root tip. This will help you • keep track of your replicates • detect any problems with a particular onion

  9. Data Collection When you are completely finished with a slide preparation, place it in the Broken Glass Disposal Container at the front of the lab room. Teams leaving slides at their station will be docked 5 points.

  10. Data Analysis: Mitotic Index The Mitotic Index(M) represents the proportion/frequency of mitotic cells in your cell population. M = nm/N • nm = the number of mitotic cells in the sample (i.e., those not in interphase) • N= the total number of cells counted in the sample.

  11. Data Analysis: Mitotic Index Why might it be useful to compare mitotic indices between treatment and control groups?

  12. Data Analysis: Mitotic Phase Index A Mitotic Phase Index (MP) can be calculated for each mitotic phase you encounter. For example: MP= np/nm • np= the number of mitotic cells in prophase in the sample • nm = the total number of mitotic cells in the sample

  13. Data Analysis: Mitotic Index Why might it be useful to compare mitotic phase indices between treatment and control groups? Do you need to compare all phases between treatment and control? Which phases would be most useful to compare, given your hypothesis?

  14. Data Analysis: Mitotic Index Before you leave lab today, calculate mitotic indices for each of your samples. • Four control onion root tips • Four treatment onion root tips Enter them in a table. Table templates are linked in the syllabus.

  15. Tabulate Mitotic Indices

  16. Data Analysis: Mitotic Phase Index Decide which Mitotic Phase Indices (MP) to use for control and treatment comparison… • Prophase • Metaphase • Anaphase • Telophase • Interphase Tabulate your indices in the table templates provided (linked in the syllabus).

  17. Example: Metaphase Mitotic Phase Index

  18. Your Indices are Your Data Mitotic Indices and Mitotic Phase Indices of • treatment samples • control samples …are the data you will statistically analyze with a Mann-Whitney U test once all your data are collected. Make sure each team member has access to a copy of his/her team’s index calculations before leaving lab. (Shared documents are good for this.)

  19. Questions?