Mastering biology chapter 12

If there are 20 centromeres in a cell at anaphase, how many chromosomes are there in each daughter cell following cytokinesis?

10

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

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

32

Motor proteins require which of the following to function in the movement of chromosomes toward the poles of the mitotic spindle?

ATP as an energy source

During which phase of mitosis do the chromatids become chromosomes?

Anaphase

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

A particular cell has half as much DNA as some other cells in a mitotically active tissue. The cell in question is most likely in

G1.

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.

At which phase are centrioles beginning to move apart in animal cells?

Prophase

Some cells have several nuclei per cell. How could such multinucleated cells be explained?

The cell underwent repeated mitosis, but cytokinesis did not occur

Several organisms, primarily protists, have what are called intermediate mitotic organization. These protists are intermediate in what sense?

They maintain a nuclear envelope during division.

Why do some species employ both mitosis and meiosis, whereas other species use only mitosis?

They need both if they are producing animal gametes.

Several organisms, primarily protists, have what are called intermediate mitotic organization. What is the most probable hypothesis about these intermediate forms of cell division?

They show some but not all of the evolutionary steps toward complete mitosis.

A cleavage furrow is _____.

a groove in the plasma membrane between daughter nuclei

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

What is the final result of mitosis in a human?

genetically identical somatic cells containing 46 chromosomes

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

in the S phase of the cell cycle

In some organisms, such as certain fungi and algae, cells undergo the cell cycle repeatedly without subsequently undergoing cytokinesis. What would result from this?

large cells containing many nuclei

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

normal growth and cell function

Which of the following does NOT occur during mitosis? spindle formation replication of the DNA condensation of the chromosomes separation of the spindle poles

replication of the DNA

Which of the following does not occur during mitosis? replication of the DNA separation of sister chromatids spindle formation condensation of the chromosomes separation of the spindle poles

replication of the DNA

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

shortening of microtubules

The beginning of anaphase is indicated by which of the following?

Cohesin is cleaved enzymatically.

In eukaryotic cells, chromosomes are composed of _____.

DNA and proteins

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

Duplicated chromosomes attach to the plasma membrane.

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

G1: follows cell division

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 actin and myosin centrioles and centromeres kinetochores

Golgi-derived vesicles

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

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? DNA synthesis spindle formation spindle attachment to kinetochores cleavage furrow formation and cytokinesis cell elongation during anaphase

cleavage furrow formation and cytokinesis

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

creating tension by pulling toward opposite poles

Nucleotides can be radiolabeled before they are incorporated into newly forming DNA and, therefore, can be assayed to track their incorporation. In a set of experiments, a studentfaculty research team used labeled T nucleotides and introduced these into the culture of dividing human cells at specific times. The research team used their experiments to study the incorporation of labeled nucleotides into a culture of lymphocytes and found that the lymphocytes incorporated the labeled nucleotide at a significantly higher level after a pathogen was introduced into the culture. They concluded that _____.

infection causes lymphocytes to divide more rapidly

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

separation of sister chromatids

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

the attachment of microtubules to kinetochores

FtsZ is a bacterial cytoskeletal protein that forms a contractile ring involved in bacterial cytokinesis. Its function is analogous to _____.

the cleavage furrow of eukaryotic animal cells

If there are 20 duplicated chromosomes in a cell, how many centromeres are there?

20

A human bone marrow cell, in prophase of mitosis, contains 46 chromosomes. How many chromatids does it contain?

92

Nucleotides can be radiolabeled before they are incorporated into newly forming DNA and, therefore, can be assayed to track their incorporation. In a set of experiments, a studentfaculty research team used labeled T nucleotides and introduced these into the culture of dividing human cells at specific times. Which of the following question might be answered by using the method described? What is the length of the S phase of the cell cycle? When do spindle fibers attach to chromosomes? How many cells are produced by the culture per hour? How many picograms of DNA are made per cell cycle?

What is the length of the S phase of the cell cycle?

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

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.

Metaphase is characterized by _____.

aligning of chromosomes on the equator

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

cells with more than one nucleus.