The cell cycle and why cells divide

Grade 9 Science Worksheet - Building Confidence

Circle the best answer.

2. 1.

   Ari reads the cell cycle wheel. In which segment is the cell's DNA copied?

   • The mitosis segment
   • The cytokinesis segment
   • The G1 segment
   • The S segment
3. 2.

   Bo watches a new cell form. It is growing and gathering building blocks, and its DNA is not copied yet. Which part of the wheel is it in?

   Use the picture in question 1.

   • G2, the second gap
   • G1, the first gap
   • M, the mitotic phase
   • No segment: a new cell rests before the cycle starts
4. 3.

   G1, S, G2, mitosis (M), cytokinesis. Jun walks clockwise around the wheel, starting at G1. Which list shows the segments in order?

   • Cytokinesis, mitosis, G2, S, G1
   • G1, S, G2, cytokinesis, mitosis
   • G1, G2, S, mitosis, cytokinesis
   • G1, S, G2, mitosis, cytokinesis
5. 4.

   Luz brackets part of the wheel as interphase. Which segments belong in the bracket?

   • Mitosis alone, since mitosis is the whole cycle
   • G1, S and G2
   • No segment: interphase is a rest between cycles
   • Mitosis and cytokinesis

6. Read this first

   Four uses of cell division (facts from OpenStax Biology 2e)

   situation	what happens
   A	a sea urchin begins as 1 cell and has 16 cells after 4 rounds of cell division
   B	human epithelial cells are replaced after about 2 to 5 days on average
   C	a single-celled organism splits into 2 single-celled organisms
   D	a fertilized egg divides again and again until a person has trillions of cells

7. 5.

   Milo reads the card. Which situation shows cell division used for reproduction, not growth or replacement?

   • A: one cell becomes 16 cells in an animal
   • D: one cell becomes the many cells of a person
   • C: one cell becomes two new organisms
   • B: old epithelial cells are swapped for new ones
8. 6.

   Noah compares two cube cells. Which cell has more surface area for each unit of its volume?

   • The 1 µm cell, with a ratio of 6
   • The 3 µm cell, since 54 is more surface area than 6
   • Neither: both cubes share the same ratio
   • The 3 µm cell, because bigger cells exchange materials better
9. 7.

   A cube cell in Pia's model grows from a side of 2 µm to a side of 4 µm. What happens to its surface-area-to-volume ratio?

   • It rises, since bigger cells exchange materials better
   • It stays at 3, since the cell keeps the same shape
   • It rises, since the bigger cell has more membrane
   • It falls from 3 to 1.5, so each part of the cell gets less membrane
11. 8.

    At the G1 gate, Ren learns that a cell has damaged DNA. What happens next?

    • The cell goes on into S, since a gate cannot stop a cell
    • The cell goes straight to cytokinesis and splits
    • The cell is held at the gate while the damage is repaired
    • The cell skips ahead to mitosis
12. 9.

    Tala reads about the gate in mitosis. What must be true before the sister chromatids are pulled apart?

    Use the picture in question 8.

    • Each pair of sister chromatids is attached to the spindle
    • The cell has already divided its cytoplasm
    • The DNA has been copied for the first time
    • The cell has doubled in size
13. 10.

    “model, not to scale” Zee reads about a mature nerve cell that does not divide. Where is it in the cell cycle?

    • In interphase, resting before its next division
    • In G0, outside the active cycle
    • In G1, getting ready to divide again soon
    • In mitosis, stuck partway through dividing