How one cell becomes two (mitosis)

Grade 7 Science Worksheet

Circle the best answer.

1. Read this first

   Use this

   Row of cards for one dividing model root-tip cell (plant), in jumbled order, not to scale (model data: 6 chromosomes). Card P: the 6 chromosomes sit in a line across the middle of the cell. Card Q: a new wall is forming across the middle of the cell, making two cells, and each has its own nucleus. Card R: the copies of each chromosome are pulled into two groups, with 6 moving toward each end. Card S: the 6 chromosomes are short, thick rods, and the boundary around the nucleus is breaking up.

2. 1.

   Luz puts four cards of one dividing root-tip cell in order, first to last. Which order is right?

   • S, P, Q, R
   • P, S, R, Q
   • S, P, R, Q
   • S, R, P, Q

3. Use this

   Row of cards for one dividing model gut-lining cell (animal), in jumbled order, not to scale (model data: 6 chromosomes). Card P: a group of 6 chromosomes sits at each end, and each group has a new nucleus boundary around it. Card Q: the 6 chromosomes sit in a line across the middle of the cell. Card R: the cell is pinched in the middle into two cells, and each has its own nucleus. Card S: the copies of each chromosome are pulled into two groups, with 6 moving toward each end.

4. 2.

   Tala puts four cards of one dividing gut-lining cell in order, first to last. Which order is right?

   • Q, P, S, R
   • Q, S, P, R
   • S, Q, P, R
   • Q, S, R, P

5. Lab note (model data)

   a root-tip cell has 6 chromosomes. The copies of each chromosome are being pulled toward the two ends of the cell. The cell has not divided yet.

6. 3.

   Esme's class reads a lab note about one root-tip cell. Which stage does the note describe?

   • Telophase
   • Anaphase
   • Metaphase
   • Cytokinesis
7. 4.

   Ren's class counts cells on a plant slide. Which cell is in a stage of mitosis, and why?

   • Cell 1, because growing and copying are the first stage of mitosis
   • Cell 2, because lining up the chromosomes is part of mitosis
   • Both cells, because a cell is in mitosis for its whole life
   • Neither cell, because mitosis is the cell splitting in two

8. Use this

   not to scale

9. 5.

   Ari sees card Q of a dividing model cell. Which stage comes next?

   • Metaphase
   • Cytokinesis
   • Telophase
   • Prophase
10. 6.

    Pia reads card S. Cytokinesis comes next. What will the new cells hold?

    • 1 cell with 20 chromosomes
    • 2 cells with 10 chromosomes each
    • 2 cells with 5 chromosomes each
    • 2 cells with 20 chromosomes each
11. 7.

    Noah watches a model plant cell in telophase. How will this boxy cell divide its cytoplasm next?

    • The chromosomes line up across the middle again
    • The cell pinches in the middle until it splits in two
    • A new wall grows across the middle between the two nuclei
    • The nucleus boundary breaks up again
12. 8.

    Jun reads that cells in zone P of a root tip keep dividing by mitosis. What does this do for the plant?

    • It adds new cells, which then grow longer and lengthen the root
    • It makes the old cells grow longer without adding new cells
    • It cuts the chromosomes in each cell in half
    • It makes egg and sperm cells for the plant

13. Gut lining, not to scale (model data)

    Row P shows cells at the surface that wear off as food moves through. Row Q shows nearby cells just under them.

14. 9.

    Kira reads that cells lining an animal's gut wear off as food moves through. How are they replaced?

    • Nearby cells divide by mitosis, making new cells with the same chromosomes
    • Nearby cells divide and share half of their chromosomes with each new cell
    • Nearby cells grow bigger until they fill the gap without dividing
    • Nearby cells divide to make egg and sperm cells that fill the gap

15. Use this

    One card of a model animal cell before it divides, not to scale (model data: 12 chromosomes). Card P: the 12 chromosomes are thin, tangled threads inside a round nucleus.

16. 10.

    Bo reads that a model animal cell with 12 chromosomes divides by mitosis to replace a worn cell. How many chromosomes should the new cell have, and why?

    • 6, because the 12 chromosomes are shared out between the new cells
    • 24, because the copies are kept and added to the originals
    • 12, because each new cell needs a full copy of the instructions
    • 18, because the cell copies half of its chromosomes