BIO151 Ch 12.1-12.2 Quiz

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

cleavage furrow formation and cytokinesis

A group of cells is assayed for DNA content immediately following mitosis and is found to have an average of 8 picograms of DNA per nucleus. How many picograms would be found at the end of S and the end of G2?

16; 16

If there are 20 chromatids in a cell which is in the G1 phase, how many centromeres are there?

20

Starting with a fertilized egg (zygote), a series of five cell divisions would produce an early embryo with how many cells?

32

What is the correct chromosomal condition at prometaphase (before metaphase) of mitosis?

B

In eukaryotic cells, chromosomes are composed of ________.

DNA and proteins

What is the correct chromosomal condition for one daughter nucleus at telophase of mitosis (not meiosis)?

E

Measurements of the amount of DNA per nucleus were taken on a large number of cells from a growing fungus. The measured DNA levels ranged from 3 to 6 picograms per nucleus. In which stage of the cell cycle did the nucleus contain 6 picograms of DNA?

G2

Which of the following are primarily responsible for cytokinesis in plant cells but not in animal cells?

Golgi-derived vesicles

How is plant cell cytokinesis different from animal cell cytokinesis?

Plant cells deposit vesicles containing cell-wall building blocks on the metaphase plate; animal cells form a cleavage furrow.

Myosin is a motor protein involved in animal cell cytokinesis. It binds to ATP or ADP, causing the myosin to move with respect to actin. What is the effect of the interaction between myosin and actin?

The cleavage furrow deepens.

Researchers pulsed rapidly dividing cultured cells with radioactive thymidine for 30 minutes. The cells were then exposed to a solution containing non-radiolabeled thymidine. Cells were analyzed at 2-hour intervals. At the 2-hour time point, no cells appeared to be in the mitosis (M) phase. Only after 4 hours did some labeled cells appear to be in M phase. This result can be explained in the following way:

There seems to be a gap or a lag in the cell cycle, between the synthesis of DNA and cell division.

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 plant cell in the process of cytokinesis

Which cytoskeletal proteins are important constituents of the contractile structures that form the cleavage furrows involved in animal cell cytokinesis?

actin

During which phase of mitosis do the two sister chromatids become independent chromosomes?

anaphase

In the cells of some organisms, mitosis occurs without cytokinesis. This results in ________.

cells with more than one nucleus

The microtubule-organizing center found in animal cells is an identifiable structure present during all phases of the cell cycle. Specifically, it is known as the ________.

centrosome

Kinetochore microtubules assist in the process of splitting centromeres by ________.

creating tension by pulling toward opposite poles

Mitosis separates chromosomes. Cytoplasm is divided between two daughter cells by ________.

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 ________.

disruption of mitotic spindle formation

If the cell whose nuclear material is shown in the accompanying figure continues toward completion of mitosis, which of the following events would occur next?

formation of telophase nuclei

Scientists isolate cells in various phases of the cell cycle. They find a group of cells that have 1.5x times more DNA than G1 phase cells. The cells of this group are ________.

in the S phase of the cell cycle

A cell in late anaphase of mitosis will have ________.

no chromosomes in the center of the cell

The first gap in the cell cycle (G1) corresponds to ________.

normal growth and cell function

At which phase are the two centrosomes beginning to move apart in animal cells?

prophase

Which of the following does NOT occur during mitosis?

replication of the DNA

The mitotic spindle is a microtubular structure that is involved in ________.

separation of sister chromatids

Movement of the chromosomes during anaphase would be most affected by a drug that prevents ________.

shortening of microtubules

In human and many other eukaryotic species' cells, the nuclear membrane has to disappear to permit ________.

the attachment of microtubules to kinetochores

Taxol is an anticancer drug extracted from the Pacific yew tree. In animal cells, Taxol disrupts microtubule formation. Surprisingly, this stops mitosis. Specifically, Taxol must affect ________.

the structure of the mitotic spindle