This worksheet helps students identify the stages of mitosis and the cell cycle through labeled diagrams and guided questions.

Let’s go step by step through each question. I’ll think carefully and check my answers before writing them down.

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Question 1: Cells A & F show an early and a late stage of the same phase of the cell cycle. What phase is it?

- Cell A: Chromosomes are condensing, nuclear envelope still there, spindle starting to form → early prophase
- Cell F: Chromosomes fully condensed, aligned at center? Wait — no, in F they’re not yet aligned; actually, looking again: In F, chromosomes are attached to spindle fibers and moving toward center? Actually, let’s compare:

Wait — better approach: Both A and F have visible chromosomes and spindles, but nucleus is breaking down or gone. Actually, both are in prophase, just different stages.

In A: Nucleus still mostly intact, chromosomes just becoming visible → early prophase
In F: Nuclear envelope gone, chromosomes more condensed, spindle fully formed → late prophase (sometimes called prometaphase)

But many textbooks group prometaphase under prophase for simplicity. So answer: Prophase

✔ Confirmed: A = early prophase, F = late prophase/prometaphase → same phase: Prophase

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Question 2: Which cell is in metaphase?

Metaphase = chromosomes lined up at equator (middle) of cell.

Look at diagram C: Chromosomes are neatly aligned in the middle → that’s metaphase.

Diagram E? No — E has sister chromatids being pulled apart → that’s anaphase.

So only C shows metaphase.

✔ Answer: C

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Question 3: Which cell is in interphase?

Interphase = cell not dividing, nucleus intact, chromatin loose (not condensed into chromosomes).

Diagram D: Has clear nucleus with nucleolus, no visible chromosomes, no spindle → this is interphase.

Others all show some sign of division.

✔ Answer: D

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Question 4: In cell A, what structure is labeled X?

X points to the star-shaped structures at opposite poles — those are centrosomes (or centrioles inside them). In animal cells, centrosomes organize spindle fibers.

Label X is pointing to the entire aster-like structure → commonly called centriole or centrosome.

Most school texts say “centriole” when pointing to the pair of barrel-shaped organelles.

Looking at diagram: X is pointing to one of the two centrosomal regions with radiating microtubules → so likely centriole or centrosome.

Standard answer expected: Centriole

✔ But technically, the whole structure including microtubules is the centrosome. However, since it's labeled on the dot/structure at pole, probably centriole.

Actually, in many diagrams, "X" pointing to the pole structure = centriole

I’ll go with centriole

Wait — let me double-check: In cell A, X is pointing to the structure from which spindle fibers emerge → that’s the centrosome, which contains centrioles.

But in high school bio, they often call it “centriole”.

To be safe: Most worksheets expect centriole

✔ Final decision: Centriole

*(Note: If teacher prefers precision, it could be centrosome — but given level, centriole is acceptable)*

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Question 5: List the diagrams in order from first to last in the cell cycle.

We need to arrange A–F in correct mitotic + cytokinesis order.

Start with interphase → then prophase → metaphase → anaphase → telophase/cytokinesis.

From earlier:

- D = interphase → FIRST
- A = early prophase
- F = late prophase/prometaphase
- C = metaphase
- E = anaphase (chromatids separating)
- B = telophase + cytokinesis (two nuclei forming, cleavage furrow)

So order: D → A → F → C → E → B

Check:

D (interphase)
A (prophase start)
F (prophase end / prometaphase)
C (metaphase)
E (anaphase)
B (telophase + cytokinesis)

Yes.

✔ Answer: D, A, F, C, E, B

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Question 6: Are the cells depicted plant or animal cells?

Look for clues:

- Cleavage furrow in B → pinching in → characteristic of animal cells
- Centrioles present (in A, F, etc.) → animal cells have them; most plants don’t
- No cell plate formation → would see in plant cells during cytokinesis
- Round shape, no rigid walls

So definitely animal cells

A. Explain your answer: Because they show cleavage furrow during cytokinesis (cell B), and have centrioles organizing spindle fibers — features typical of animal cells.

B. If it were the other type (plant), what would be different?

→ Instead of cleavage furrow, you’d see a cell plate forming in the middle during cytokinesis.

→ Also, plant cells usually lack centrioles (though some do have them — but generally taught as absent).

→ Shape might be more rectangular due to cell wall.

✔ Answers:

6. Animal cells
A. They have cleavage furrows and centrioles, which are found in animal cells.
B. Plant cells would form a cell plate instead of a cleavage furrow, and typically lack centrioles.

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Question 7: What is the longest phase of the cell cycle?

Interphase includes G1, S, G2 — together make up ~90% of cell cycle.

Even though mitosis looks dramatic, it’s short.

Longest single phase? Interphase as a whole.

Sometimes asked as “which part of interphase?” — but here says “phase of the cell cycle”, so interphase.

✔ Answer: Interphase

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Question 8: State three reasons why mitosis is important for a healthy organism.

Mitosis makes identical daughter cells.

Reasons:

1. Growth — multicellular organisms grow by increasing number of cells via mitosis.
2. Repair — damaged tissues replaced by new cells made through mitosis.
3. Replacement — old/dying cells (like skin, blood) constantly replaced via mitosis.

Also: Asexual reproduction in some organisms — but maybe stick to human/body context.

✔ Three reasons:

- For growth of the organism
- To repair damaged tissues
- To replace worn-out or dead cells

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Question 9: What is happening in G1 and G2?

G1 = Gap 1 → after mitosis, before DNA synthesis. Cell grows, makes proteins/organelles, prepares for DNA replication.

G2 = Gap 2 → after DNA synthesis, before mitosis. Cell grows more, checks DNA, makes proteins needed for division (like tubulin for spindle).

S phase is between them — DNA replicated.

So:

G1: Cell grows and carries out normal functions; prepares for DNA replication.

G2: Cell continues growing; produces molecules needed for mitosis; checks DNA for errors.

✔ Answer:

In G1, the cell grows and performs its regular jobs while preparing to copy its DNA.
In G2, the cell finishes growing, makes tools for division (like spindle parts), and double-checks that DNA was copied correctly.

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Question 10: Predict what would happen if cells divided uncontrollably.

Uncontrolled cell division → too many cells → forms masses/tumors.

If benign → harmless lump.

If malignant → cancer → invades nearby tissue, spreads (metastasizes).

Can disrupt organ function, cause illness or death.

✔ Answer: Uncontrolled cell division can lead to tumors and cancer, which may damage organs and spread throughout the body, causing serious health problems or death.

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Now, compiling final answers clearly.

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Final Answer:

1. Prophase
2. C
3. D
4. Centriole
5. D, A, F, C, E, B
6. Animal cells
A. The cells show cleavage furrows during cytokinesis and have centrioles, which are characteristic of animal cells.
B. Plant cells would form a cell plate instead of a cleavage furrow and usually lack centrioles.
7. Interphase
8. - Allows organisms to grow by adding more cells
- Repairs damaged tissues
- Replaces old or dead cells
9. In G1, the cell grows and prepares for DNA copying. In G2, the cell grows more, makes materials for division, and checks that DNA was copied correctly.
10. Uncontrolled cell division can cause tumors and cancer, leading to organ damage, spreading disease, and potentially death.