Microsoft word - d28 onionkey.doc

Name ________Key________________
Lab: Onion Root Mitosis
Answer each question in complete sentences as part of your lab report write-up in the
Analysis section. Analysis section should be in paragraph format!
1. What evidence did you observe that shows that the cell cycle is a continuous process, not a series of separate events?
Some of the cells are in an “in between phase”. For example, they are not really in
prophase, or in metaphase, but somewhere in the middle. This demonstrates that
the cell cycle is a continuous process, with in between steps.

2. Why did we make our graphs based on the class data, and why is it important to answer all Analysis and Conclusion questions based on class data rather than the data for your individual group?
The class data is more accurate than individual data because it is like running the
experiment several times. It is unlikely that the same error would happen in every
group, so running the experiment several times helps to “even out” the errors.

3. Based on the Class Percentage (not your Group Count), what was the most common phase (include numbers from data)? What does the difference in numbers of cells at each phase mean? (Of the five stages of the cell cycle, which takes the longest to complete? Which is the shortest?)
The most common phase is interphase because ________________ (refer to the
class data.) The phase with the most cel s is the longest, and the phase with the
least cells is the shortest. (It’s usually metaphase, but it will depend on the class

Remind students that they should take their answers to this section, and put them
in paragraph format for their formal lab write-ups.

Conclusion Questions:
Answer each question in complete sentences as part of your lab report write-up in the
Conclusion section. Conclusion section should be in paragraph format!
1. Were you looking at animal cells or plant cells in this lab? What about the cells you were looking at would clearly show what kind of cell you were looking at even if you didn't have other clues? You can tell that you are looking at plant cells during this lab because they are
square-shaped, and plant cells are usually square-shaped.

2. Cells in the root divide many times as the root grows longer and thicker. With each cell division, the chromosomes are divided between two daughter cells, yet the number of chromosomes in each cell does not change. What process ensures that the normal number of chromosomes is restored after each cell division? (In other words, why don’t the daughter cells end up with half of the parent cell’s DNA?) During which part of the cell cycle does this process occur? DNA replication (or the copying of DNA) ensures that the daughter cells end up with
the same number of chromosomes as the parent cell. DNA replication occurs during
the S phase of interphase.

3. Scientists have divided the cell cycle into five major phases (interphase, prophase, metaphase, anaphase, telophase), each characterized by important events, but these divisions are fairly arbitrary. Scientists could have chosen to divide the cell cycle up in a variety of different ways. Why is it beneficial that scientists agreed upon one accepted version of the phases of the cell cycle?
It’s helpful that scientists agree upon one accepted version of the cel cycle so that
scientists in different countries can all communicate about the cell cycle and know
what each other are talking about.
Please remind students that these answers will satisfy part L of their lab rubrics.
They also need to take care of the other rubric requirements for their Conclusions.
(letters J, K, M)


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