Mitiosis Internet Lesson Key | PDF | Mitosis | Cell Cycle - Free Printable

This image is a worksheet for a Regents Biology lab on "Cell Division: Mitosis in Onion Root Tips." The main task is to identify the stages of mitosis shown in the diagram at the bottom, which are numbered 1 through 9.

I will solve this by identifying each stage based on its visual characteristics and then matching it to the correct name from my knowledge of the cell cycle.

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Step 1: Identify Stage 1

- Visual Description: The cell has a clearly defined nucleus with chromatin that is not yet condensed into visible chromosomes. The nuclear envelope is intact.
- Analysis: This is the stage before mitosis begins, where the cell is preparing for division. DNA replication occurs during this phase.
- Conclusion: This is Interphase.

Step 2: Identify Stage 2

- Visual Description: The chromatin has started to condense into visible, thread-like chromosomes. The nuclear envelope is beginning to break down.
- Analysis: This is the first stage of mitosis, characterized by chromosome condensation and the breakdown of the nuclear envelope.
- Conclusion: This is Prophase.

Step 3: Identify Stage 3

- Visual Description: The chromosomes are lined up single-file along the equator (metaphase plate) of the cell. Spindle fibers are attached to the centromeres of each chromosome.
- Analysis: This is the middle stage of mitosis, where chromosomes align for separation.
- Conclusion: This is Metaphase.

Step 4: Identify Stage 4

- Visual Description: This box points to the nucleolus within the nucleus of the interphase cell.
- Analysis: While not a stage of mitosis itself, the nucleolus is a key structure that disappears during prophase and reforms during telophase. It's often labeled in diagrams to show its location before division.
- Conclusion: This label points to the Nucleolus.

Step 5: Identify Stage 5

- Visual Description: This box points to the chromosomes in the prophase cell.
- Analysis: This highlights the condensed genetic material that is becoming visible as the cell enters mitosis.
- Conclusion: This label points to the Chromosomes.

Step 6: Identify Stage 6

- Visual Description: This box points to the spindle fibers attached to the chromosomes in the metaphase cell.
- Analysis: These are the microtubules that pull the chromosomes apart.
- Conclusion: This label points to the Spindle Fibers.

Step 7: Identify Stage 7

- Visual Description: The sister chromatids (now individual chromosomes) are being pulled apart to opposite poles of the cell.
- Analysis: This is the stage where the actual separation of genetic material occurs.
- Conclusion: This is Anaphase.

Step 8: Identify Stage 8

- Visual Description: The chromosomes have reached the opposite poles of the cell. They are starting to decondense, and new nuclear envelopes are forming around them.
- Analysis: This is the final stage of mitosis, where two new nuclei are formed.
- Conclusion: This is Telophase.

Step 9: Identify Stage 9

- Visual Description: Two distinct daughter cells are shown, each with its own nucleus and cytoplasm.
- Analysis: This represents the completion of cell division, which includes both mitosis (nuclear division) and cytokinesis (cytoplasmic division).
- Conclusion: This is Cytokinesis.

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Final Answer

Here are the correct labels for each numbered box in the "Stages of Mitosis" diagram:

1. Interphase
2. Prophase
3. Metaphase
4. Nucleolus
5. Chromosomes
6. Spindle Fibers
7. Anaphase
8. Telophase
9. Cytokinesis

This sequence accurately depicts the process of mitotic cell division, from the preparatory interphase through the four main stages of mitosis (Prophase, Metaphase, Anaphase, Telophase) and concluding with cytokinesis, which results in two genetically identical daughter cells.