CH 12 HW

As in most areas of biology, the study of mitosis and the cell cycle involves a lot of new terminology. Knowing what the different terms mean is essential to understanding and describing the processes occurring in the cell.

Drag the terms on the left to correctly complete these sentences. Not all the terms will be used.

• 1. DNA replication produces two identical DNA molecules, called sister chromatid(s), which separate during mitosis.

  2.After chromosomes condense, the centromere(s) is the region where the identical DNA molecules are most tightly attached to each other.

  3. During mitosis, microtubules attach to chromosomes at the kinetochore(s)

  4. In dividing cells, most of the cell's growth occurs during interphase

  5. The mitotic spindle(s) is a cell structure consisting of microtubules, which forms during early mitosis and plays a role in cell division

• The mitotic spindle(s) is a cell structure consisting of microtubules, which forms during early mitosis and plays a role in cell division.

  6. During interphase, most of the nucleus is filled with a complex of DNA and protein in a dispersed form called chromatin.

  7. In most eukaryotes, division of the nucleus is followed by cytokinesis, when the rest of the cell divides.

  8. The centrosome(s) are the organizing centers for microtubules involved in separating chromosomes during mitosis.

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The cell cycle represents the coordinated sequence of events in the life of a cell from its formation to its division into two daughter cells. Most of the key events of the cell cycle are restricted to a specific time within the cycle. In this exercise, you will identify when various events occur during the cell cycle. Recall that interphase consists of the G1, S, and G2 subphases, and that the M phase consists of mitosis and cytokinesis.

Drag each label to the appropriate target.

• A) non-dividing cells exit cell cycle

  B) at this point, cell commits to go through the cycle

• C)DNA replicated.

  D) Two centrosomes have formed.

• E) Mitotic Spindle begins to form

  F) Cells divided

As the chromosomes of a parent cell are duplicated and distributed to the two daughter cells during cell division, the structure of the chromosome's changes. Answer the three questions for each phase of the cell cycle by dragging the yes and no labels to the appropriate locations in the table .Note: Assume that by the end of the M phase, the parent cell has not yet divided to form two daughter cells.

• Are sister chromatid present in all or part of this phase?G1-no S-yes G2-yes Beginning of M-yes End of M-no

• Is the DNA condensed in all or part of this phase?

  G1- no S-no G2-no Beginning of M-yes End of M-yes

• Does the cell contain twice as much DNA in this phase as it did in the G1 phase?

  G1- no S-yes G2-yes Beginning of M- yes End of M-yes

The stages of mitosis were originally defined by cellular features observable through a light microscope. The six micrographs below show animal cells (lung cells from a newt) during the five stages of mitosis, plus cytokinesis. (Note that interphase is not represented in these micrographs.) In these images, the chromosomes have been stained blue, microtubules green, and microfilaments red.

Drag each micrograph to the target that indicates the stage of mitosis or cytokinesis it shows.

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• EASY

Mitosis unfolds through a sequence of stages marked by specific events in the cell. The structural changes in the cell are brought about by a series of tightly coordinated underlying mechanisms.

Sort each process into the appropriate bin to indicate the stage of mitosis in which it occurs. If a process occurs in more than one stage, sort it to the stage when it first occurs.

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• YAY

The mitotic spindle consists of two types of microtubules: kinetochore microtubules and nonkinetochore microtubules. In animal cells, these two types of microtubules function differently in the stages of mitosis.

Complete the sentences by dragging the terms to the appropriate locations. Terms may be used once, more than once, or not at all.

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• beep

Consider three questions concerning the animal cell that has been treated with the inhibitor. Drag the terms to answer the questions. Terms may be used once, more than once, or not at all.

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• bbbo

In all cells, separation of replicated chromosomes is a prerequisite for cell division. However, the mechanism of chromosome separation in bacteria is distinct from that in eukaryotes in several ways.

• Bacteria only: Chromosome separation begins at the origin of replication on DNA.

• Eukaryotes only: Before separation, duplicated chromosomes condense; Nuclear envelope fragments, permitting chromosome separation; Two copies of the duplicated chromosome are attached at their centromeres before separating.

• Both bacteria and eukaryotes: Replicated chromosomes separate by attaching to some other structural feature of the cell; Chromosomes replicate before cell division.

Cytokinesis in animal cells is accomplished by constriction of the cell along the plane of cell division (formation of a cleavage furrow). In plant cells, which have cell walls, a completely different mechanism of cytokinesis has evolved.

Which of the following statements are true of cytokinesis in plant cells? Select the two that apply.

• In plant cell division, after chromosome separation, the microtubules of the mitotic spindle reorganize into a network that guides vesicles derived from the Golgi apparatus to the plane of cell division. These vesicles begin to fuse, forming the cell plate. As more vesicles are added to the cell plate, it grows outward, eventually fusing with the parent cell plasma membrane. Membrane from the vesicles forms the new plasma membrane for each daughter cell. At the same time, materials that were enclosed in the vesicles form the new cell wall between the new plasma membranes of the daughter cells.

• In plant cell division, after chromosome separation, the microtubules of the mitotic spindle reorganize into a network that guides vesicles derived from the Golgi apparatus to the plane of cell division. These vesicles begin to fuse, forming the cell plate. As more vesicles are added to the cell plate, it grows outward, eventually fusing with the parent cell plasma membrane. Membrane from the vesicles forms the new plasma membrane for each daughter cell. At the same time, materials that were enclosed in the vesicles form the new cell wall between the new plasma membranes of the daughter cells.

• The cell plate consists of the plasma membrane and cell wall that will eventually separate the two daughter cells.

Plant and animal cells also require cytoskeletal proteins for cytokinesis, although the roles these proteins play differ among bacteria, plants, and animals.

For each space in the table, drag the appropriate label to indicate if the statement is true or false for each group of organisms.

• 1. Bacteria: true

  Animals: true

  Plants: false

• 2. Bacteria: false

  Animals: false

  Plants: true

• 3. Bacteria: true

  Animals: false

  Plants: true