Chapter 12

Which of the following is found in binary fission but not in mitosis? (A) Duplicated chromosomes attach to the plasma membrane. (B) The result produces 2 nuclei. (C) Replicated strands of DNA separate. (D) Following the process, a membrane separates the 2 copies. (E) Replication of DNA begins at an origin.

(A) Duplicated chromosomes attach to the plasma membrane

Through a microscope, you can see a cell plate beginning to develop across the middle of a cell and nuclei forming on either side of the cell plate. This cell is most likely (A) a plant cell in the process of cytokinesis. (B) an animal cell in the S phase of the cell cycle. (C) a plant cell in metaphase. (D) a bacterial cell dividing. (E) an animal cell in the process of cytokinesis

(A) a plant cell in the process of cytokinesis.

Which of the following is true of kinetochores? (A) They are the primary centromere structures that maintain the attachment of the sister chromatids prior to mitosis. (B) They are sites at which microtubules attach to chromosomes. (C) They interdigitate at the cell's equator and then move apart, causing the cell to elongate. (D) They are located at the center of the centrosome; their function is to organize tubulin into elongated bundles called spindle fibers. (E) They attach to the ring of actin along the cytoplasmic surface of the plasma membrane, causing the actin to contract to form the cleavage furrow.

(B) They are sites at which microtubules attach to chromosomes.

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) metaphase. (B) G2. (C) G1. (D) prophase.

(C) G1

Cells will usually divide if they receive the proper signal at a checkpoint in which phase of the cell cycle? (A) cytokinesis (B) M (C) G1 (D) S (E) G2

(C) G1

Why is it difficult to observe individual chromosomes with a light microscope during interphase? (A) They leave the nucleus and are dispersed to other parts of the cell. (B) The spindle must move them to the metaphase plate before they become visible. (C) They have uncoiled to form long, thin strands. (D) The DNA has not been replicated yet. (E) Sister chromatids do not pair up until division starts.

(C) They have uncoiled to form long, thin strands.

Which of the following is true of benign tumors, but not malignant tumors? (A) They are the result of the transformation of normal cells. (B) They can divide indefinitely if an adequate supply of nutrients is available. (C) They remain confined to their original site (D) They have an unusual number of chromosomes. (E) They migrate from the initial site of transformation to other organs or tissues.

(C) They remain confined to their original site

In the cells of some organisms, mitosis occurs without cytokinesis. This will result in (A) cells lacking nuclei. (B) destruction of chromosomes. (C) cells with more than one nucleus. (D) cells that are unusually small. (E) cell cycles lacking an S phase.

(C) cells with more than one nucleus.

Which of the following does not occur during mitosis? (A) spindle formation (B) separation of sister chromatids (C) replication of the DNA (D) separation of the spindle poles (E) condensation of the chromosomes

(C) replication of the DNA

A human bone marrow cell, in prophase of mitosis, contains 46 chromosomes. How many chromatids does it contain? (A) 23 or 46, depending on the portion of prophase examined (B) 46 or 92, depending on the portion of prophase examined (C) 23 (D) 92 (E) 46

(D) 92

Which of the following correctly matches a phase of the cell cycle with its description? (A) S: immediately precedes cell division (B) G2: cell division (C) M: duplication of DNA (D) G1: follows cell division (E) All of the above are correctly matched.

(D) G1: follows cell division

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) DNA synthesis (B) spindle formation (C) cell elongation during anaphase (D) cleavage furrow formation and cytokinesis (E) spindle attachment to kinetochores

(D) cleavage furrow formation and cytokinesis

Vinblastine is a standard chemotherapeutic drug used to treat cancer. Because it interferes with the assembly of microtubules, its effectiveness must be related to (A) inhibition of regulatory protein phosphorylation. (B) suppression of cyclin production. (C) inhibition of DNA synthesis. (D) disruption of mitotic spindle formation. (E) myosin denaturation and inhibition of cleavage furrow formation.

(D) disruption of mitotic spindle formation.

One difference between cancer cells and normal cells is that cancer cells (A) are always in the M phase of the cell cycle. (B) are unable to synthesize DNA. (C) cannot function properly because they are affected by density-dependent inhibition. (D) are arrested at the S phase of the cell cycle. (E) continue to divide even when they are tightly packed together.

(E) continue to divide even when they are tightly packed together.

In some organisms, such as certain fungi and algae, cells undergo the cell cycle repeatedly without subsequently undergoing cytokinesis. What would result from this? (A) a decrease in chromosome number (B) division of the organism into many cells, most lacking nuclei (C) a rapid rate of gamete production (D) inability to duplicate DNA (E) large cells containing many nuclei

(E) large cells containing many nuclei