What is the primary purpose of a checkpoint in the cell cycle?

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

Cytochalasin B is a chemical that disrupts microfilament formation. This chemical would interfere with:

a. DNA replication

b. Formation of the mitotic spindle

c. Cleavage

d. Formation of the cell plate

Discuss the factors that control the division of eukaryotic cells grown in the laboratory. Cancer cells are easier to grow in the lab than other cells.

Why do you suppose this is?