Chapter 12 Quiz
attachment of microtubules to kinetochores
In the cells of many eukaryotic species, the nuclear envelope has to disappear to permit which of the following events in the cell cycle? - attachment of microtubules to kinetochores - separation of the centrosomes - condensation of the chromosomes - DNA synthesis
cells with more than one nucleus
In the cells of some organisms, mitosis occurs without cytokinesis. This will result in
No; the DNA content per cell changes as the S phase progresses, so the cells in S phase have a range of fluorescence levels.
In the control sample histogram, does the population of cells in the S phase show a distinct peak? Why or why not? Yes; all of the cells have to pass through the S phase to get from G1 to G2. No; the DNA content per cell changes as the S phase progresses, so the cells in S phase have a range of fluorescence levels. No; the S phase is inhibited in the control sample. Yes; the DNA content per cell is increasing during S phase.
Eukaryotes only
- before separation duplicated chromosomes condense - nuclear envelope fragments permitting chromosome separation - 2 copies of the duplicated chromosome are attached at their centromeres before separating
bacterias and eukaryotes
- replicated chromosomes separate by attaching to some other structural feature of the cell - chromosomes replicate before cell division
16
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 of DNA would be found in a nucleus at prophase of mitosis? - 24 -8 -4 -16
92
A human bone marrow cell, in prophase of mitosis, contains 46 chromosomes. How many chromatids does it contain? See Concept 12.1 (Page) 23 or 46, depending on the portion of prophase examined 46 23 92 or 46, depending on the portion of prophase examined 92
- lack of appropriate cell death
Besides the ability of some cancer cells to over proliferate, which of the following situations might logically result in a tumor? - failure of cells to enter S phase - inability to form spindles - changes in the order of cell cycle stages - lack of appropriate cell death
g1
Cell A has half as much DNA as cells B, C, and D in a mitotically active tissue. Cell A is most likely in - prophase - metaphase - g2 - g1
Cell cycle checkpoints are not in place to stop cells with chromosome abnormalities.
Cells from advanced malignant tumors often have very abnormal chromosomes and an abnormal number of chromosomes. What might explain the association between malignant tumors and chromosomal abnormalities? - Cancer cells are no longer density-dependent. - Cancer cells are no longer anchorage-dependent. - Transformation introduces new chromosomes into cells. - Cell cycle checkpoints are not in place to stop cells with chromosome abnormalities.
G1
Cells will usually divide if they receive the proper signal at a checkpoint in which phase of the cell cycle? See Concept 12.3 (Page) - g1 - s -cytokinesis - g2 - m
anaphase
Centromeres divide and sister chromatids become full-fledged chromosomes during _____. - anaphase - prophase - telophase - metaphase - interphase - prometaphase
Bacteria Only
Chromosome separation begins at the origin of replication of DNA
Cleavage
Cytochalasin B is a chemical that disrupts microfilament formation. How would this interfere with cell division? See Concept 12.2 (Page) - cleavage - formation of the mitotic spindle - formation of the cell plate - DNA replication - binary fission
- As cells become more numerous, they begin to squeeze against each other, restricting their size and ability to allow cell growth
Density-dependent inhibition is a phenomenon in which crowded cells stop dividing at some optimal density and location. This phenomenon involves binding of a cell-surface protein to its counterpart on an adjoining cell's surface. A growth inhibiting signal is sent to both cells, preventing them from dividing. Certain external physical factors can affect this inhibition mechanism. Select the statement that makes a correct prediction about natural phenomena that could occur during the cell cycle to prevent cell growth. - As cells become more numerous, more and more of them enter the synthesis part of the cell cycle and duplicate DNA to inhibit cell growth. - As cells become more numerous, the protein kinases they produce begin to compete with each other until only one cell has the proteins necessary for growth. - As cells become more numerous, the amount of required growth factors and nutrients per cell becomes insufficient to allow for cell growth. - As cells become more numerous, they begin to squeeze against each other, restricting their size and ability to allow cell growth
- As cells become more numerous, the cell surface proteins of one cell contact the adjoining cells, and they signal each other to stop dividing.
Density-dependent inhibition is explained by which of the following processes? - As cells become more numerous, the level of waste products increases, which slows metabolism and inhibits growth. - As cells become more numerous, the protein kinases they produce begin to compete with each other, such that the proteins produced by one cell essentially cancel those produced by its neighbor. - As cells become more numerous, the cell surface proteins of one cell contact the adjoining cells, and they signal each other to stop dividing. - As cells become more numerous, they begin to squeeze against each other, restricting their size.
the mitotic phase (M)
During _____ both the contents of the nucleus and the cytoplasm are divided.
interphase
During _____ the cell grows and replicates both its organelles and its chromosomes. - interphase - g1 - s - mitosis - cytokinesis
anaphase
During which phase of mitosis do the chromatids become chromosomes? - prophase - anaphase - metaphase - telophase
The cells show characteristics of tumors.
Early observations of a cultured cell line indicated that the cells did not exhibit either density-dependent inhibition or anchorage dependence. What do these observations suggest about this cell line? -The cells have nonfunctional MPF. - The cells are unable to form spindle microtubules. - The cells show characteristics of tumors. - The cells follow an altered series of cell cycle phases.
normal growth and cell function
G1 is associated with which of the following cellular events? -normal growth and cell function - break down of the nuclear membrane - the beginning of mitosis - DNA replication
large cells containing many nuclei
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 decrease in chromosome number a rapid rate of gamete production inability to duplicate DNA large cells containing many nuclei division of the organism into many cells, most lacking nuclei
cancer cells may be immortal
How do cancer cells differ from normal cells?
a: g1, b: s, c: g2
Identify which phase of the cell cycle is represented by each region. The regions represent the same cell cycle phases in both histograms.
10
If a cell at metaphase of mitosis contains 20 sister chromatids, how many chromosomes will be present in a G1 cell? - 40 -10 - 5 -20
Each chromosome is made of a complex of DNA and associated proteins.
If a eukaryotic cell is in the G1 phase of the cell cycle, which statement about the cell's chromosomes must be correct? - The chromosomes are preparing for DNA synthesis. - Each chromosome consists of two identical chromatids. - Each chromosome is made of a complex of DNA and associated proteins.
20
If there are 40 centromeres in a cell at anaphase of mitosis, how many chromosomes will be found in each daughter cell following cytokinesis? - 80 -40 -20 -10
24
In a diploid cell with 6 chromosome pairs (2n = 12), how many chromatids will be found in a nucleus at prophase of mitosis? - 12 -6 -24 -48
Cytokinesis when the cytoplasm divides forming two new cells.
In a dividing cell, the mitotic (M) phase alternates with interphase (I), a growth period. - S when the DNA replicates to make two copies. - G2 when a gap forms separating the chromosomes into two areas in the cell. - G1 where the cell grows and duplicates cellular organelles. - Cytokinesis when the cytoplasm divides forming two new cells.
g2
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? - s -g1 - g2 - g0
shortening of microtubules
Movement of the chromosomes during anaphase would be most affected by a drug that prevents - shortening of microtubules - enlongation of microtubules - formation of a cleavage furrow - nuclear envelope breakdown
interphase
Nucleoli are present during _____. - anaphase - prophase - telophase - metaphase - interphase - prometaphase
- The cyclin component of MPF is degraded.
Once a cell enters mitosis, the molecules that activate division must be turned off. What happens to MPF during mitosis? - It is phosphorylated by a Cdk, which inactivates it. - The cyclin component of MPF is degraded. - The Cdk component of MPF is degraded. - It is completely degraded.
continue to divide even when they are tightly packed together.
One difference between cancer cells and normal cells is that cancer cells
prometaphase
Spindle fibers attach to kinetochores during _____. - anaphase - prophase - telophase - metaphase - interphase - prometaphase
the mitotic spindle
Taxol is an anticancer drug extracted from the Pacific yew tree. In animal cells, Taxol prevents microtubule depolymerization. Thus, Taxol stops mitosis by interfering with which of the following structures or processes? - the mitotic spindle centriole duplication chromosome condensation cytokinesis
metaphase
The M phase checkpoint ensures that all chromosomes are attached to the mitotic spindle. If this does not happen, cells would most likely be arrested in ________. - g2 - metaphase - telophase - prophase
Enzymatic cleavage of cohesin.
The beginning of anaphase is indicated by which of the following processes? - Enzymatic cleavage of cohesin. - Attachment of sister chromatids to each other by cohesin. - Loss of kinetochores from the chromatids. - Disappearance of the nuclear membrane.
Genetic changes alter the function of the cancer cell's protein products.
The cell cycle control systems of cancer cells differ from those of normal cells. Select the best explanation for this fact. Genetic changes alter the function of the cancer cell's protein products. Cancer cells divide excessively and invade other tissues. Cancer cells are immortal.
the degradation of cyclin.
The decline of MPF activity at the end of mitosis is due to
- cleavage furrow formation and cytokinesis
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? - cleavage furrow formation and cytokinesis - spindle formation - DNA synthesis - cell elongation during anaphase - spindle attachment to kinetochores
The cells would enter mitosis.
What would you expect to happen if MPF (maturation-promoting factor) is introduced into immature frog oocytes that are arrested in G2? - The cells would remain arrested in G2. - The cells would begin DNA synthesis. - The cells would enter mitosis. - The cells would enter G0.
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 - an animal cell in the S phase of the cell cycle. - a bacterial cell dividing. - a plant cell in the process of cytokinesis. - a plant cell in metaphase. - an animal cell in the process of cytokinesis. Submit
disruption of mitotic spindle formation.
Vinblastine is a standard chemotherapeutic drug used to treat cancer. Because it interferes with the assembly of microtubules, its effectiveness must be related to inhibition of regulatory protein phosphorylation. disruption of mitotic spindle formation.
centrosome
What is the name of the microtubule-organizing center found in animal cells as an identifiable structure present during all phases of the cell cycle? - centriole - centrosome - kinetochore - centromere
They have escaped normal cell cycle controls.
What is true of all cancers?
The inhibitor might block the activity of a cyclin or signaling molecule of the G1 checkpoint.
Which mechanism is the best explanation for how the stem cell-derived inhibitor might arrest the cancer cell cycle at the G1 stage? The inhibitor might block the activity of a cyclin or signaling molecule of the G2 checkpoint. The inhibitor might block the activity of a cyclin or signaling molecule of the G1 checkpoint. The inhibitor might block release of a stimulatory growth factor from a cyclin of the G1 checkpoint. The inhibitor might block assembly of the mitotic spindle.
G1: follows cell division
Which of the following correctly matches a phase of the cell cycle with its description? See Concept 12.2 (Page) G1: follows cell division M: duplication of DNA G2: cell division S: immediately precedes cell division All of the above are correctly matched.
replication of the DNA
Which of the following does not occur during mitosis?
Duplicated chromosomes attach to the plasma membrane.
Which of the following is found in binary fission but not in mitosis? See Concept 12.2 (Page) Following the process, a membrane separates the 2 copies. Duplicated chromosomes attach to the plasma membrane. Replicated strands of DNA separate. Replication of DNA begins at an origin. The result produces 2 nuclei.
They remain confined to their original site
Which of the following is true of benign tumors, but not malignant tumors? - They can divide indefinitely if an adequate supply of nutrients is available. - They migrate from the initial site of transformation to other organs or tissues. - They remain confined to their original site - They are the result of the transformation of normal cells. - They have an unusual number of chromosomes.
They are sites at which microtubules attach to chromosomes.
Which of the following is true of kinetochores? See Concept 12.2 (Page) - They are sites at which microtubules attach to chromosomes. They are located at the center of the centrosome; their function is to organize tubulin into elongated bundles called spindle fibers. They are the primary centromere structures that maintain the attachment of the sister chromatids prior to mitosis. They interdigitate at the cell's equator and then move apart, causing the cell to elongate. 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.
- Vesicles from the Golgi apparatus move along microtubules, coalesce at the plane of cell division, and form a cell plate. - The cell plate consists of the plasma membrane and cell wall that will eventually separate the two daughter cells.
Which of the following statements are true of cytokinesis in plant cells? Select the two that apply. - Vesicles from the Golgi apparatus move along microtubules, coalesce at the plane of cell division, and form a cell plate. - The cell plate consists of the plasma membrane and cell wall that will eventually separate the two daughter cells. - After chromosome separation is complete, a network of microfilaments forms near the plane of cell division that will separate the two new cells. - The plasma membrane of the parent cell grows inward, eventually joining with the cell plate.
all of the above are carcinogens
Which of these is NOT a carcinogen? testosterone UV light cigarette smoke fat all of the above are carcinogens
mitosis (E)
Which of these phases includes all of the stages of mitosis but no other events?
During interphase, a cell is metabolically active.
Which statement provides the best description of the interphase portion of the cell cycle? - During interphase, a cell is metabolically active. - Interphase is a brief period between mitosis and chromosome duplication. - Interphase is a resting stage prior to cell division.
They have uncoiled to form long, thin strands.
Why is it difficult to observe individual chromosomes with a light microscope during interphase? See Concept 12.1 (Page) Sister chromatids do not pair up until division starts. They have uncoiled to form long, thin strands. The DNA has not been replicated yet. They leave the nucleus and are dispersed to other parts of the cell. The spindle must move them to the metaphase plate before they become visible.
true for bacteria and animals
cells divide by constriction of a ring of protein
prophase
chromosomes become visible during - anaphase - prophase - telophase - metaphase - interphase - prometaphase
telophase
cytokinesis often but not always accompanies - - anaphase - prophase - telophase - metaphase - interphase - prometaphase
true for plants
the presence of a cell wall prevents the cell from dividing by constriction
true for bacteria and plants
tubulin function in binary fission (bacteria) or cytokinesis (animals and plants)
