Chapter 9
Beginning with a fertilized egg (zygote), how many cells would be present in an embryo following a series of five cell divisions? A: 32 B: 16 C: 8 D: 4 E: 64
A: 32
What is the difference between a benign tumor and a malignant tumor? A: Cells of benign tumors do not metastasize; those of malignant tumors do. B: Cells of benign tumors metastasize; those of malignant tumors do not. C: Benign tumors do not arise by transformation; malignant tumors do. D: Benign tumors will not kill you; malignant tumors will. E: Benign tumors arise by transformation; malignant tumors do not.
A: Cells of benign tumors do not metastasize; those of malignant tumors do.
When a cell in S phase is fused with a cell in G1, __________. A: DNA synthesis begins immediately in the original G1nucleus B: the chromosomes of the original G1 nucleus condense in preparation for mitosis C: the original G1 cell will divide immediately D: the replication of DNA occurring in the original S nucleus is terminated E: the two nuclei fuse and further division is arrested
A: DNA synthesis begins immediately in the original G1nucleus
Which of the following molecules or structures are primarily responsible for cytokinesis in plant cells but not in animal cells? A: Golgi-derived vesicles B: actin and myosin C: centrioles and centromeres D: spot desmosomes E: tubulin and dynein
A: Golgi-derived vesicles
What is true of all cancers? A: They have escaped normal cell cycle controls. B: They are caused by chemical carcinogens. C: They are inherited.
A: They have escaped normal cell cycle controls. Read about the consequences of escaping the cell cycle.
During interphase, the genetic material of a typical eukaryotic cell is __________. A: dispersed in the nucleus as long strands of chromatin B: dispersed in the cytoplasm as long strands of chromatin C: attached to microtubule spindle fibers D: transported through the nuclear pores E: condensed, and the chromosomes are often visible under the light microscope
A: dispersed in the nucleus as long strands of chromatin
Observations of cancer cells in culture support the hypothesis that cancer cells __________. A: do not exhibit density-dependent inhibition B: spend the majority of their time in the G0 phase C: produce molecules that inhibit the growth factors D: All of the listed responses are correct. E: exhibit anchorage dependence
A: do not exhibit density-dependent inhibition Cancer cells divide uncontrollably; they do not produce molecules that inhibit growth factors. Rather than pausing in the G0 phase, cancer cells pass through S phase and proceed through cell division. Cancer cells are characterized by a lack of anchorage dependence.
Sister chromatids are __________. A: identical copies of a chromosome B: the bacterial equivalent of eukaryotic chromosomes C: held together by the centrioles D: found only in aberrant chromosomes E: present throughout the cell cycle
A: identical copies of a chromosome
In a human skin cell that is going through the cell cycle, when do the centrosomes separate? A: prophase B: metaphase C: G2 phase D: anaphase E: S phase
A: prophase
Following DNA replication, each eukaryotic chromosome consists of two identical DNA molecules known as A: sister chromatids B: sister cohesins C: sister chromatins D: daughter chromosomes
A: sister chromatids
Down syndrome is characterized by cells having three copies of chromosome 21. As a somatic cell in an individual with Down syndrome prepares to enter mitosis, how many chromatids would be present in the cell's nucleus? A: 23 B: 94 C: 98 D: 46 E: 92
B: 94
Which of the following does not occur during mitosis? A: Movement of chromosomes toward opposite poles of the cell B: Duplication of chromosomes C: Condensation of chromatin D: Separation of chromatids E: Alignment of chromosomes along the cell's equatorial plane
B: Duplication of chromosomes
Cells will usually divide if they receive the proper signal at a checkpoint in which phase of the cell cycle? A: M B: G1 C: cytokinesis D: S E: G2
B: G1 In mammalian cells, the G1 checkpoint is termed the restriction point.
Why do most cells in the human body divide infrequently? A: They no longer have active nuclei. B: They have exited the cell cycle and entered G0. C: They no longer carry receptors for signal molecules. D: They have defective microtubules.
B: They have exited the cell cycle and entered G0.
The beginning of anaphase is indicated by which of the following events? A: loss of kinetochores from sister chromatids B: enzymatic cleavage of cohesin C: polymerization of spindle microtubules D: joining of the sister chromatids to each other by cohesin
B: enzymatic cleavage of cohesin
Where are the motor proteins that move chromosomes toward the poles of the mitotic spindle located? A: at the centrosomes only B: on the kinetochores only C: on the kinetochores and at the centrosomes D: along the length of kinetochore microtubules only
B: on the kinetochores only
In telophase of mitosis, the mitotic spindle breaks down and the chromatin uncoils. This is essentially the opposite of what happens in __________. A: S phase B: prophase C: interphase D: anaphase E: metaphase
B: prophase
One event occurring during prophase is __________. A: the synthesis of a new nuclear envelope B: the beginning of the formation of a mitotic spindle C: the alignment of chromosomes in a single plane D: separation of sister chromatids E: cytokinesis
B: the beginning of the formation of a mitotic spindle
Following cytokinesis in an animal cell, how many centrioles does each new daughter cell possess? A: 0 B: 1 C: 2 D: 4 E: 8
C: 2
During which phase in the cell cycle would you find the most DNA per cell? A: G1 B: S1 C: G2 D: S E: prophase II
C: G2
Which of the following processes does not occur in dividing bacteria? A: Separation of the origins of replication B: Binary fission C: Mitosis D: Inward growth of the plasma membrane E: Replication of DNA
C: Mitosis Prokaryotes can undergo a type of reproduction in which the cell grows to roughly double its size and then divides to form two cells. The term binary fission, meaning "division in half," refers to this process.
In a human skin cell that is going through the cell cycle, when do the centrosomes separate? A: S phase B: Metaphase C: Prophase D: G2 phase E: Anaphase
C: Prophase The S phase and G2 phase are part of interphase and not part of mitosis. During prophase, the chromatin of the chromosomes condenses so that they appear distinct within the nucleus, and the mitotic spindle begins to form. The mitotic spindle consists of fibers made of microtubules and associate proteins and serves as a dynamic scaffolding associated with movement of chromosomes within the cell. In prometaphase, the nuclear envelope fragments and microtubules of the mitotic spindle invade the nuclear area. Alignment of chromosomes along the cell's equatorial plane occurs during metaphase. Sister chromatids separate in anaphase of mitosis, at which point they are no longer called sister chromatids but are considered individual chromosomes that move toward opposite poles of the cell. In telophase, a nucleus forms around the set of chromosomes that will make up the genome of each daughter cell.
The person credited with the axiom, "Every cell from a cell" is __________. A: James Watson B: Anton van Leeuwenhoek C: Rudolf Virchow D: Louis Pasteur E: Robert Hooke
C: Rudolf Virchow Louis Pasteur conclusively falsified the hypothesis of life arising by spontaneous generation. Robert Hooke was the discoverer of the cell. Anton van Leeuwenhoek discovered single-celled organisms. Along with Francis Crick and Rosalind Franklin, James Watson determined the structure of DNA.
Which of the following is true of kinetochores? A: They interdigitate at the cell's equator and then move apart, causing the cell to elongate. B: 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. C: They are sites at which microtubules attach to chromosomes. D: They are located at the center of the centrosome; their function is to organize tubulin into elongated bundles called spindle fibers. E: They are the primary centromere structures that maintain the attachment of the sister chromatids prior to mitosis.
C: 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.
What is a cleavage furrow? A: a ring of vesicles forming a cell plate B: an indentation between daughter prokaryotic cells C: a groove in the plasma membrane between daughter nuclei D: the metaphase plate where chromosomes attach to the spindle
C: a groove in the plasma membrane between daughter nuclei
Where do the microtubules of the spindle originate during mitosis in animal cells? A: chromatid B: centromere C: centrosome D: kinetochore E: centriole
C: centrosome
The complex of DNA and protein that makes up a eukaryotic chromosome is properly called __________. A: a centrosome B: actin C: chromatin D: a centromere E: a chromatid
C: chromatin
Cytokinesis refers to __________. A: duplication of the cell's chromosomes B: division of the nucleus C: division of the cytoplasm D: alignment of chromosomes E: movement of sister chromatids to opposite ends of the cell
C: division of the cytoplasm
If the cell whose nuclear material is shown in the figure above continues toward completion of mitosis, which of the following events would occur next?(양 끝으로 당겨서 분열 중) A: synthesis of sister chromatids B: formation of telophase nuclei C: segregation of daughter chromosomes toward the poles D: cell membrane synthesis E: alignment of chromosomes at the metaphase plate
C: segregation of daughter chromosomes toward the poles
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? A: 14 B: 28 C: None of the listed responses is correct. D: 0 E: 7
D: 0 Assume that you are dealing with a species in which the number of chromosomes in each somatic cell is 14. In the early telophase of mitosis, there will be 0 sister chromatids present. During interphase of the cell cycle, all of a eukaryotic cell's chromosomes are duplicated. Each duplicated chromosome has two sister chromatids, which are joined copies of the original chromosome. Each sister chromatid has a centromere, a region containing specific DNA sequences, where the chromatid is attached most closely to its sister chromatid. Once separated during anaphase of mitosis, the chromatids become full-fledged chromosomes that move toward opposite ends of the cell. Therefore, in the last stage of mitosis, telophase, there are no longer any chromatids present.
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 each contained 200 units of DNA. What would be the amount of DNA at G1 of the cell cycle in a daughter cell of one of these cells? A: 50 units B: 400 units C: 200 units D: 100 units E: Between 50 and 100 units
D: 100 units During interphase, a cell that is about to divide grows and copies its chromosomes in preparation for cell division. Interphase can be divided into subphases: the G1 phase ("first gap"), the S phase ("synthesis"), and the G2 phase ("second gap"). Chromosomes are duplicated only during the S phase. Each duplicated chromosome has two sister chromatids, which are joined copies of the original chromosome. If a cell is to divide, it then undergoes mitosis, the division of genetic material. Sister chromatids separate during anaphase of mitosis and become full-fledged chromosomes that move toward opposite ends of the cell. Cytokinesis, the splitting of the cell, results in daughter cells that each have half of these chromosomes, and therefore half of the DNA, that was present in the cell from which they arose.
Somatic cells in elephants have 56 chromosomes. How many chromosomes would be carried by the gametes produced by elephants? A: 112 B: 14 C: 56 D: 28
D: 28
If a human somatic cell is in metaphase, it has __________ chromatids. A: 23 B: 0 C: There is insufficient information to answer the question D: 92 E: 46
D: 92
Which of the following components make(s) up eukaryotic chromatin? A: DNA and carbohydrates B: DNA and RNA C: condensed DNA only D: DNA and proteins E: DNA and ribosomes
D: DNA and proteins
A cell entering mitosis with 32 chromosomes will produce daughter cells with __________. A: 6 chromosomes B: 64 chromosomes C: 64 pairs of chromosomes D: None of the listed responses is correct. E: 32 pairs of chromosomes
D: None of the listed responses is correct. Every eukaryotic species has a characteristic number of chromosomes in each cell nucleus. For example, the nuclei of human somatic cells (all body cells except the reproductive cells) each contain 46 chromosomes, made up of two sets of 23, one set inherited from each parent. Reproductive cells, or gametes—sperm and eggs—have half as many chromosomes as somatic cells, or one set of 23 chromosomes in humans. During the cell cycle, all of the chromosomes are duplicated. A cell that enters the cell cycle with 32 chromosomes would have 64 chromosomes prior to mitosis. Mitosis distributes the chromosomes evenly to the two daughter cells. Daughter cells produced through mitosis have the same number of chromosomes as the parent cell from which they are produced.
Humans produce skin cells by mitosis and gametes by meiosis. Which of the following statements about the nuclei of skin cells is correct? A: They contain the same amount of DNA as the nuclei of gametes produced by meiosis. B: They contain half as much DNA as the nuclei of gametes produced by meiosis. C: They contain four times as much DNA as the nuclei of gametes produced by meiosis. D: They contain twice as much DNA as the nuclei of gametes produced by meiosis.
D: They contain twice as much DNA as the nuclei of gametes produced by meiosis.
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 have an unusual number of chromosomes. C: They can divide indefinitely if an adequate supply of nutrients is available. D: They remain confined to their original site. E: They migrate from the initial site of transformation to other organs or tissues.
D: 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.
At which phase of mitosis do the sister chromatids become daughter chromosomes? A: metaphase B: prophase C: prometaphase D: anaphase E: cytokinesis
D: anaphase
You would know a dividing cell was a plant cell rather than an animal cell if you saw that __________. A: it had microtubules B: it had formed a cleavage furrow C: it had two pairs of centrioles during prophase D: it had formed a cell plate E: chromatin was condensed into chromosomes visible through a microscope
D: it had formed a cell plate In animal cells, cytokinesis occurs by a process known as cleavage. Cytokinesis in plant cells, which have cell walls, is markedly different. There is no cleavage furrow. Instead, during telophase, vesicles derived from the Golgi apparatus move along microtubules to the middle of the cell, where they coalesce, producing a cell plate. Cell wall materials carried in the vesicles collect in the cell plate as it grows. The cell plate enlarges until its surrounding membrane fuses with the plasma membrane along the perimeter of the cell. Two daughter cells result, each with its own plasma membrane. Both plant and animal cells have microtubules and chromosomes visible through a microscope (beginning in prophase of mitosis), but plant cells lack centrioles.
One event occurring during prophase is __________. A: the synthesis of a new nuclear envelope B: division of the centromere C: cytokinesis D: the beginning of the formation of a spindle apparatus E: the alignment of chromosomes in a single plane
D: the beginning of the formation of a spindle apparatus
When not engaged in the processes leading to cell division, how many chromosomes from your mother are present in the nucleus of each of your somatic cells? A: 184 B: 92 C: 46 D: None of the listed responses is correct. E: 23
E: 23
A human bone marrow cell, in prophase of mitosis, contains 46 chromosomes. How many chromatids does it contain? A: 46 or 92, depending on the portion of prophase examined B: 46 C: 23 D: 23 or 46, depending on the portion of prophase examined E: 92
E: 92
The cleavage furrow forms during which stage of mitosis and cell division of an animal cell? A: Telophase B: Prophase C: Anaphase D: Metaphase E: Cytokinesis
E: Cytokinesis
Which of the following represents a mismatch or incorrect description? A: Anaphase: there is movement of the chromosomes toward opposite poles of the cell B: Prophase: chromatin becomes more tightly coiled C: Metaphase: chromosomes line up on the equatorial plane D: Telophase: nuclei form E: Metaphase: the nuclear envelope disappears
E: Metaphase: the nuclear envelope disappears
You would be unlikely to see which of the following human cells dividing? A: Skin cell B: Embryonic cell C: Cancer cell D: Cell of the intestinal lining E: Nerve cell
E: Nerve cell If a cell receives a go-ahead signal at the G1 checkpoint, it will usually complete the G1, S, G2, and M phases and divide. If it does not receive a go-ahead signal at that point, it will exit the cycle, switching into a nondividing state called the G0 phase. Most cells of the human body are actually in the G0 phase. Skin cells divide regularly in response to damage and the natural loss of the surface cells. Cancer cells are characterized by the failure to recognize or respond to the signals that prevent cell division. Cells in embryos are constantly dividing, allowing the embryo to grow. The lining of the intestine and surfaces that directly contact the external environment are replaced quite regularly.
The function of mitosis and cytokinesis is to produce daughter cells that __________. A: None of the listed responses is correct. B: have the same number of chromatids as the parent cell had chromosomes C: have a random assortment of maternal and paternal chromosomes D: have the same number of chromosomes as the parent cell but unique genetic content E: are genetically identical to the parent cell
E: are genetically identical to the parent cell
A biochemist measured the amount of DNA in cells growing in the laboratory and found that the quantity of DNA in the cells doubled __________. A: between prophase and anaphase B: during the M phase of the cell cycle C: between the G2 phase and prophase D: between anaphase and telophase E: between the G1 and G2 phases
E: between the G1 and G2 phases
Which is involved in the binary fission of bacteria? A: disintegration of the nuclear membrane B: formation of a cell plate C: prophase, prometaphase, metaphase, anaphase, and telophase D: formation of a spindle apparatus E: distribution of a copy of the single parental chromosome to each daughter cell
E: distribution of a copy of the single parental chromosome to each daughter cell
Tissue culture experiments with PDGF demonstrate that without this substance __________. A: various kinases are unable to bind to cyclin B: cells divide in an uncontrolled fashion, confirming PDGF's role as a cell division inhibitor C: animal cells are unable to attach to the substratum D: bacterial cells will not proliferate E: fibroblasts fail to divide
E: fibroblasts fail to divide PDGF is a growth factor, not a cell division inhibitor. Growth factors are functional in multicellular organisms. Bacteria are unicellular and reproduce via binary fission after growing to a certain size. Animal cells must attach to a stratum in order to divide, but PDGF does not play a role in this. Many cyclin-dependent kinases participate in regulating cell division, but PDGF is not involved.
What will be the result if a eukaryotic cell completes mitosis but does not undergo cytokinesis? A: one cell with one nucleus containing half of the genetic material of the parent cell B: two cells, each cell with half of the genetic material of the parent cell C: two cells, one cell containing two nuclei and a second cell without a nucleus D: one cell with two nuclei, each containing half of the genetic material of the parent cell E: one cell with two nuclei, each identical to the nucleus of the parent cell
E: one cell with two nuclei, each identical to the nucleus of the parent cell
During binary fission of a bacterium, __________. A: genetic material is acquired from another bacterium B: the nuclear envelope fragments C: chromosomes are separated through attachment to a mitotic spindle D: a small daughter cell buds from a large parent cell E: origins of replication move apart
E: origins of replication move apart The process of cell division is initiated when the DNA of the bacterial chromosome begins to replicate at a specific place on the chromosome called the origin of replication, producing two origins. As the chromosome continues to replicate, one origin moves rapidly toward the opposite end of the cell. While the chromosome is replicating, the cell elongates. When replication is complete and the bacterium has reached about twice its initial size, its plasma membrane pinches inward, dividing the parent cell into two daughter cells. In this way, each cell inherits a complete genome.
Movement of the chromosomes during anaphase would be most affected by a drug that prevents which of the following processes? A: formation of a cleavage furrow B: cell wall formation C: nuclear envelope breakdown D: elongation of microtubules E: shortening of microtubules
E: shortening of microtubules
Which phase of mitosis is essentially the opposite of prometaphase in terms of the nuclear envelope? A: metaphase B: anaphase C: S phase D: interphase E: telophase
E: telophase
DNA replication occurs in __________. A: prophase of both mitosis and meiosis B: metaphase of meiosis only C: the cytokinesis portion of the cell's life cycle D: the G1 phase of interphase in reproductive cells only E: the S phase of interphase in both somatic and reproductive cells
E: the S phase of interphase in both somatic and reproductive cells
