Which of the following occurs during S phase?
a. Condensation of the chromosomes
b. Replication of the DNA
c. Separation of sister chromatids
d. Spindle formation

The drug cytochalasin B blocks the function of actin. Which of the following aspects of the animal cell cycle would be most disrupted by cytochalasin B?

a. Spindle formation

b. Spindle attachment to kinetochores

c. Cell elongation during anaphase

d. Cleavage furrow formation and cytokinesis

The light micrograph shows dividing cells near the tip of an onion root. Identify a cell in each of the following stages: prophase, prometaphase, metaphase, anaphase, and telophase. Describe the major events occurring at each stage.

<IMAGE>

In the cells of some organisms, mitosis occurs without cytokinesis. This will result in

a. Cells with more than one nucleus

b. Cells that are unusually small

c. Cells lacking nuclei

d. Cell cycles lacking an S phase

Cell A has half as much DNA as cells B, C, and D in a mitotically active tissue. Cell A is most likely in

a. G1

b. G2

c. Prophase

d. Metaphase

The decline of MPF activity at the end of mitosis is due to

a. The destruction of the protein kinase Cdk

b. Decreased synthesis of Cdk

c. The degradation of cyclin

d. The accumulation of cyclin

Which of the following occurs during apoptosis?

a. Lysis of the cell

b. Direct contact between signaling cells

c. Fragmentation of the DNA

d. Release of proteases outside the cell