Chapter 12 Questions Flashcards Preview

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Flashcards in Chapter 12 Questions Deck (84)

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


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


One difference between cancer cells and normal cells is that cancer cells

continue to divide even when they are tightly packed together


The decline of MPF activity at the end of mitosis is due to

the degradation of cyclin


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

cells with more than one nucleus


Which of the following does NOT occur during mitosis?

replication of DNA


Which of the following DOES occur in mitosis?

-condensation of the chromosomes
-separation of sister chromatids
-spindle formation
-separation of the spindle pores


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



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


The function of the mitotic cell cycle is to produce daughter cells that _____.

are genetically identical to the parent cell (assuming no mutation has occurred)

-Cell division involves the distribution of identical genetic material (DNA) to two daughter chromosomes.


Which of the following is true regarding sister chromatids?

-sister chromatids are separated during mitosis
-sister chromatids form in the S-phase stage of the cell cycle
-sister chromatids are attached to one another at the centromere
-sister chromatids are created when DNA is replicated


The complex of DNA and protein that makes up a eukaryotic chromosome is properly called _____.


-The DNA-protein complex called chromatin is organized into a long, thin fiber.


The region of a chromosome holding the two double strands of replicated DNA together is called _____.

a centromere

-The chromosome has a narrow "waist" at a specialized region, called the centromere, where the two chromatids are attached to each other.


The centromere is a region in which _____.

sister chromatids are attached to one another in prophase

-The chromosome has a narrow "waist" at a specialized region called the centromere, where sister chromatids are attached.


How many maternal chromosomes are present in a somatic human cell not engaged in cell division?


-Human somatic cells contain a total of 46 chromosomes, half of which are maternally derived.


A cell entering the cell cycle with 32 chromosomes will produce two daughter cells, each with _____.

There would be 32 chromosomes present in each of the daughter cells.


"Cytokinesis" refers to _____.

division of the cytoplasm

-Cytokinesis is the division of the cytoplasm that follows the mitotic division of the nucleus.


Chromatids are _____.

identical copies of each other if they are part of the same chromosome

-Each duplicated chromosome consists of two identical sister chromatids.


If a cell contains 60 chromatids at the start of mitosis, how many chromosomes will be found in each daughter cell at the completion of the cell cycle?


-In this case, mitosis starts with 30 chromosomes, each of which consists of two chromatids. At the completion of mitosis, each daughter cell will contain 30 chromosomes.


A biochemist measured the amount of DNA in cells growing in the laboratory and found that the quantity of DNA in the cells doubled _____.

between the G1 and G2 phases

-Between these two phases of the cell cycle, the DNA is replicated during the S phase.


A cell biologist carefully measured the quantity of DNA in grasshopper cells growing in cell culture. Cells examined during the G2 phase of the cell cycle contained 200 units of DNA. What would be the amount of DNA at G1 of the cell cycle in one of the grasshopper daughter cells?

100 units

-Recall that G2 follows S and that during the S phase, DNA is replicated.


During interphase, the genetic material of a typical eukaryotic cell is _____.

dispersed in the nucleus as long strands of chromatin


DNA replication occurs in _____.

the S phase of interphase in both somatic and reproductive cells

-Chromosomes are duplicated only during the S phase ("S" stands for synthesis of DNA).


If a somatic human cell is just about to divide, it has _____ chromatids.



Down syndrome is characterized by cells having three copies of chromosome 21. As a cell in an individual with Down syndrome prepares to enter mitosis, how many chromatids would be present?


-Cells from an individual with Down syndrome would have 23 pairs of chromosomes, plus an extra chromosome for a total of 47. At S phase those chromosomes replicate to produce 94 sister chromatids.


Which of the following does NOT occur during mitosis?

replication of chromosomes

-The DNA of the chromosomes is replicated in the S phase before mitosis.


During what phase in the cell cycle would you find the most DNA per cell?


-Chromosomes are duplicated only during the S phase ("S" stands for synthesis of DNA). The phase following completion of the S phase is G2.


In telophase of mitosis, the mitotic spindle breaks down and the chromatin uncoils. This is essentially the opposite of what happens in _____.


-During prophase, we observe the formation of the spindle, the condensation of chromatin, and the disappearance of the nucleolus.


Which of the following phases of mitosis is essentially the opposite of prometaphase in terms of the nuclear envelope?


-In prometaphase the nuclear envelope fragments and the kinetochores attach to microtubules. During telophase, fragments of the nuclear envelope begin to reassemble along with portions of the endomembrane system.


Assume that you are dealing with a species in which the number of chromosomes in each somatic cell is 14. How many sister chromatids are present in the early telophase of mitosis?



In a human skin cell that is going through the cell cycle, when do the centrosomes separate?



Following cytokinesis in an animal cell, how many centrioles does each new daughter cell possess?


-Each daughter cell inherits a single centrosome following cytokinesis and each centrosome contains two centrioles.


The phase of mitosis during which the chromosomes move toward separate poles of the cell is _____.



One event occurring during prophase is _____.

the beginning of the formation of a spindle apparatus

-During prophase, the mitotic spindle begins to form.


Which event or events occur during anaphase?

-the centrioles are at opposite poles
-the centromeres divide
-a spindle made of microtubules is present
-identical chromatids move to opposite poles


Which of the following represents a match of descriptions?

-anaphase: there is movement of the chromosomes to the poles
-telophase: chromosomes become more extended
-prophase: chromosomes become more tightly coiled
-metaphase: chromosomes line up on the equatorial plane


During which stage of the cell cycle do sister chromatids separate?



In animal cell mitosis, the cleavage furrow forms during which stage of the cell cycle?



At which stage of mitosis are chromosomes lined up in one plane in preparation for their separation to opposite poles of the cell?


-The chromosomes convene on the metaphase plate, an imaginary plane that is equidistant from the spindle's two poles.


You would know a dividing cell was a plant cell rather than an animal cell if you saw that _____.

it had formed a cell plate

-The cell plate, which divides the cytoplasm in two, forms during the telophase of mitosis in a plant cell.


Which of the following processes does NOT occur in dividing bacteria?


-Mitosis does not occur in dividing bacteria. Mitosis might have had its origins in simpler bacterial mechanisms of cell reproduction. Prokaryotes (bacteria) reproduce by a type of cell division called binary fission.


During binary fission in a bacterium _____.

the origins of replication move apart


Which of the following is involved in the binary fission of bacteria?

distribution of a copy of the single parental chromosome to each daughter cell


When a cell in S phase is fused with a cell in G1, _____.

DNA synthesis begins immediately in the original G1 nucleus


Tissue culture experiments with PDGF demonstrate that without this substance _____.

fibroblasts fail to divide


You would be unlikely to see which of the following human cells dividing?

nerve cell


Observations of cancer cells in culture support the hypothesis that cancer cells _____.

do not exhibit density-dependent inhibition

-Normal cells respond to density-dependent inhibition by growing in culture to form a single layer of cells.


What is the difference between a benign tumor and a malignant tumor?

Cells of benign tumors do not metastasize; those of malignant tumors do.

-Cells of malignant tumors spread from their site of origin to other parts of the body.


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

They need both if they are producing animal gametes.

-The form of cell division that produces animal gametes is meiosis, not mitosis. The production of gametes in plants is a function of both mitosis and meiosis


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


-Mitosis follows the duplication of the cell's DNA.


Why is it difficult to observe individual chromosomes with a light microscope during interphase?

They have uncoiled to form long, thin strands.

-Except during the M phase, the DNA is extended, allowing its genes to be transcribed for protein synthesis.


Which of the following is true of kinetochores?

They are sites at which microtubules attach to chromosomes.

-As the spindle depolymerizes, the kinetochores appear to move along the spindle fiber, dragging the attached chromosomes with them.


Which of the following correctly matches a phase of the cell cycle with its description?

G1: follows cell division

-After mitosis and cytokinesis, the newly formed daughter cells enter the G1 phase.


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


Which of the following is found in binary fission but not in mitosis?

Duplicated chromosomes attach to the plasma membrane.


Cytochalasin B is a chemical that disrupts microfilament formation. How would this interfere with cell division?


-In animal cells, the cleavage furrow forms when a ring of microfilaments contracts, causing the parent cell to be pinched in two.


Cells will usually divide if they receive the proper signal at a checkpoint in which phase of the cell cycle?


-In mammalian cells, this checkpoint is termed the restriction point


Which of the following is true of benign tumors, but not malignant tumors?

They remain confined to their original site

-Benign tumors can often be surgically removed because their boundaries are well defined, whereas some malignant tumors go on to metastasize.


Nucleoli are present during _____.



Cytokinesis often, but not always, accompanies _____.



Chromosomes become visible during _____.


-During prophase, the chromatin fibers become discrete chromosomes.


Centromeres divide and sister chromatids become full-fledged chromosomes during _____.


-During anaphase, sister chromatids separate and daughter chromosomes migrate to opposite poles.


Spindle fibers attach to kinetochores during _____.


-Attachment of spindle fibers to kinetochores is one of the events of prometaphase.


During anaphase centromeres come apart, and

sister chromatids become full-fledged chromosomes, which migrate to opposite poles of the cell.


Cytokinesis in animal cells involves

the formation of a cleavage furrow.


Events of prophase include the

condensation of chromatin and the dispersal of nucleoli.


During metaphase chromosomes

align along the metaphase plate.


The events of prometaphase include the

attachment of spindle fibers to kinetochores.


Cytokinesis in plant cells involves

the formation of a cell plate.


During telophase

both nuclear envelopes and nucleoli re-form


During prophase a homologous pair of chromosomes consists of _____.

two chromosomes and four chromatids.

-At this point each of the chromosomes consists of two chromatids.


During _____ both the contents of the nucleus and the cytoplasm are divided.

the mitotic phase

-The mitotic phase encompasses both mitosis and cytokinesis.


During _____ the cell grows and replicates both its organelles and its chromosomes.



Which of the following is a function of the S phase in the cell cycle?

The synthesis of sister chromatids

-DNA replication occurs during S phase and results in two sister chromatids for each original chromosome.


The copying of chromosomes occurs during which of the following phases of the cell cycle?

S phase

-Chromosomes must undergo replication before mitosis can occur; this copying occurs during the S phase.


For the first several divisions of early frog embryos, cells proceed directly from the M phase to the S phase and back to M without gaps. Which of the following is likely to be true about dividing cells in early frog embryos?

The cells get smaller with each generation.

-Without gap phases, the cells have no opportunity to grow.


Cells replicate their chromosomes during the

S phase and divide partition their chromosomes during the M phase.


If an organism normally has 34 chromosomes, how many molecules of DNA should there be in the G1 phase of the cell cycle?


-There is one DNA molecule per chromosome


Which of the following events would cause the cell cycle to arrest?

Poor nutrient conditions

-Poor nutrient conditions would arrest the cell cycle at the G1 checkpoint.


When cells were first taken from Henrietta Lacks, she was _____.

suffering from cervical cancer


How did doctors harvest and culture cells from Henrietta Lacks?

Cells were taken while she was being treated for cancer many years ago, and these cells have been cultured in the lab ever since.


Did doctors ask Henrietta Lacks’ permission to take her cells, and was she paid for them?

She was never told that her cells were being taken, and neither she nor her family has been compensated.


What property of Henrietta Lacks’ cells was most unusual when they were grown in the laboratory?

They continue to divide and multiply after decades of culture.


Cells taken from Henrietta Lacks have been used for experiments leading to _____.

-the development of a polio vaccine
-new treatments for cancer
-tests of the effects of atomic radiation on life