Chapter 12 bio reading quesitons

32

Beginning with a fertilized egg (zygote), how many cells will be present in the embryo following five rounds of cell division? 16 10 32 6

anaphase

In which phase of mitosis do the sister chromatids become daughter chromosomes? telophase prophase metaphase anaphase

20

A group of cells is assayed for DNA content immediately following mitosis and is found to have an average of 10 picograms of DNA per nucleus. Approximately how many picograms of DNA would be found in a nucleus at prophase of mitosis? 20 5 10 40

92

A human bone marrow cell, in prophase of mitosis, contains 46 chromosomes. How many chromatids does it contain? See Concept 12.1 (Page) View Available Hint(s)for Part A 23 23 or 46, depending on the portion of prophase examined 92 46 46 or 92, depending on the portion of prophase examined

92

A human bone marrow cell, in prophase of mitosis, contains 46 chromosomes. How many chromatids does it contain? See Concept 12.1 (Page) View Available Hint(s)for Part A 46 46 or 92, depending on the portion of prophase examined 23 92 23 or 46, depending on the portion of prophase examined

Infection causes lymphocytes to divide more rapidly. Submit

A research team used a culture of lymphocytes with radioactively labeled T nucleotides to study the cell cycle. They found that the lymphocytes incorporated the labeled nucleotide at a significantly higher rate after a pathogen was introduced into the culture. Which of the following conclusions is most consistent with the results? The pathogen consumed radiolabeled nucleotides. Infection causes lymphocytes to increase in size. Infection causes lymphocyte cultures to skip some parts of the cell cycle. Infection causes lymphocytes to divide more rapidly.

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Amount of DNA per nucleus over the cell division cycle. Which region of the accompanying figure represents S phase? I II III IV

G1

Cells will usually divide if they receive the proper signal at a checkpoint in which phase of the cell cycle? View Available Hint(s)for Part A G2 G1 M cytokinesis S

cleavage

Cytochalasin B is a chemical that disrupts microfilament formation. With which aspect of cell division would cytochalasin B interfere? View Available Hint(s)for Part A cleavage DNA replication formation of the mitotic spindle binary fission formation of the cell plate

DNA and proteins

Eukaryotic chromatin is composed of which of the following macromolecules? DNA and RNA DNA and phospholipids DNA and proteins DNA only

Cancer cells may be immortal.

How do cancer cells differ from normal cells? Cancer cells may be immortal. Cultured cancer cells exhibit anchorage dependence. Cancer cells trigger chromosomal changes in surrounding cells.

Such cells do not respond to signals that normally trigger apoptosis. Such cells are not inhibited by density. Such cells can divide in the absence of growth factors. Such cells do not require anchorage to a surface in order to divide.

How is the cell division of cancer cells like these misregulated? Select all that apply. Such cells do not respond to signals that normally trigger apoptosis. Such cells are not inhibited by density. Such cells can divide in the absence of growth factors. Such cells do not require anchorage to a surface in order to divide. Such cells do not need enzymes for DNA replication. Such cells skip the G1 phase of the cell cycle.

16

If a cell at metaphase of mitosis contains 32 sister chromatids, how many chromosomes will be present in a G1 cell? 32 64 8 16

segregation of daughter chromosomes

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 spindle formation segregation of daughter chromosomes nuclear envelope breakdown

8

In a diploid cell with four chromosome pairs (2n = 8), how many centromeres will be found in a nucleus at G2 of the cell division cycle? 8 32 4 16

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? View Available Hint(s)for Part A a decrease in chromosome number inability to duplicate DNA a rapid rate of gamete production large cells containing many nuclei division of the organism into many cells, most lacking nuclei

shortening of microtubules

Movement of the chromosomes during anaphase would be most directly affected by a drug that prevents which of the following events? elongation of microtubules nuclear envelope breakdown formation of a cleavage furrow shortening of microtubules

continue to divide even when they are tightly packed together.

One difference between cancer cells and normal cells is that cancer cells are arrested at the S phase of the cell cycle. cannot function properly because they are affected by density-dependent inhibition. continue to divide even when they are tightly packed together. are unable to synthesize DNA .

Line 2 contains more DNA than line 1.

One type of eukaryotic cell (line 1) spends 24 minutes in S phase and another type of cell (line 2) spends 48 minutes in S phase. Which of the following statements is the best explanation for the difference in time spent in S phase by cell lines 1 and 2? A diagram of the amount of D N A in the nucleus during two cell cycles. From left to right, the diagram is divided into the first cycle and the second cycle. Each cycle is divided into three approximately equal sections and one much narrower section at the end of each cycle. A graph line runs across the sections, starting halfway up the y-axis. It runs horizontally across the first section and is labeled 1. It then rises to the top of the y-axis; that line segment is labeled 2. In the third section, labeled 3, the line runs horizontally at the top of the y-axis. In the narrow section, labeled 4, the line drops sharply back to its initial level. The line then runs horizontally through the first section of the second cycle, labeled 5. The cycle continues to repeat itself. Amount of DNA per nucleus over the cell division cycle. Line 2 contains more DNA than line 1. Line 2 has plant cells and line 1 has animal cells. Lines 1 and 2 contain the same amount of DNA. Line 1 cells reproduce by binary fission and line 2 cells reproduce by mitosis and cytokinesis.

As cells become more numerous, the cell surface proteins of one cell contact the adjoining cells, and they signal each other to stop dividing.

Part complete Which of the following statements best describes density-dependent inhibition? As cells become more numerous, they begin to squeeze against each other, restricting their size. 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, the level of waste products increases, which slows metabolism and inhibits growth.

in the S phase

Students in a biology lab isolated cells in various phases of the cell cycle. A population of cells that have 1 1/2 times the DNA of G1 phase cells was most likely isolated from which of the following parts of the cell cycle? in the S phase in the G2 phase in the M phase between the G1 and S phases

During mitosis, each chromatid of a duplicated chromosome becomes attached to the microtubule of one of the mitotic spindles. At anaphase, mitotic spindles pull the chromatids toward the poles of the cell, therefore forming two identical chromosomal sets at each pole.

The continuity of life is based on heritable information in the form of DNA . How does the process of mitosis faithfully parcel out exact copies of this heritable information in the production of genetically identical daughter cells? During mitosis, each chromosome becomes attached to the centromere. At anaphase, centromeres drag random chromatids toward the poles of the cell, where they become duplicated. As a result, two identical chromosomal sets form at each pole. During mitosis, each chromatid of a duplicated chromosome becomes attached to the microtubule of one of the mitotic spindles. At anaphase, mitotic spindles pull the chromatids toward the poles of the cell, therefore forming two identical chromosomal sets at each pole. During mitosis, each duplicated chromosome becomes attached to the microtubule of one of the mitotic spindles. At anaphase, mitotic spindles pull the chromosomes toward the poles of the cell, therefore forming two identical chromosomal sets at each pole. During mitosis, each chromosome becomes attached to the centromere. At anaphase, centromeres drag random chromosomes toward the poles of the cell, where they become duplicated. As a result, two identical chromosomal sets form at each pole.

the degradation of cyclin.

The decline of MPF activity at the end of mitosis is due to decreased synthesis of Cdk. the degradation of cyclin. the destruction of the protein kinase Cdk. the accumulation of cyclin.

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The unlettered circle at the top of the accompanying figure shows a diploid nucleus with four unreplicated chromosomes. The circles labeled 1 to 5 show various combinations of these chromosomes. A circle with two chromosomes and a centromere labeled. Five numbered circles are beneath it. Circle 1 contains one long and one short haploid dark chromosomes. Circle 2 contains one long and one short diploid dark pairs of chromosomes and one long and one short diploid light pairs of chromosomes. Circle 3 contains one long diploid light pair of chromosomes and one short diploid dark black pair of chromosomes. Circle 4 contains two long diploid chromosomes, one dark pair and one light. Circle 5 contains one long haploid dark chromosome and one short haploid dark chromosome, one long haploid light chromosome and one short haploid light chromosome. Which chromosomal configuration would be observed at prometaphase of mitosis? II III IV V

disruption of mitotic spindle formation. Submit

Vinblastine is a standard chemotherapeutic drug used to treat cancer. Because it interferes with the assembly of microtubules, its effectiveness must be related to myosin denaturation and inhibition of cleavage furrow formation. suppression of cyclin production. inhibition of DNA synthesis. disruption of mitotic spindle formation.

The underlying basis for this altered behavior is a series of genetic and cellular changes, including mutations in genes whose protein products normally regulate the cell cycle. These gene products are often proteins that function in cell signaling pathways

What are the genetic or other changes that might have caused these cells to escape normal cell cycle regulation? The underlying basis for this altered behavior is a series of genetic changes, including mutations in genes whose protein products normally code the enzymes of DNA replication. The underlying basis for this altered behavior is a series of cellular changes, including misfolding of proteins that function in cell signaling pathways. The incorrect folding of mutant proteins causes their incorrect work. The underlying basis for this altered behavior is a series of genetic and cellular changes, including mutations in genes whose protein products normally code the signaling enzymes. These gene products are often proteins that function in metabolic pathways. The underlying basis for this altered behavior is a series of genetic and cellular changes, including mutations in genes whose protein products normally regulate the cell cycle. These gene products are often proteins that function in cell signaling pathways.

They have escaped normal cell cycle controls.

What is true of all cancers? They are caused by chemical carcinogens. They have escaped normal cell cycle controls. They are inherited.

G1, follows cell division

Which of the following correctly matches a phase of the cell cycle with its description? View Available Hint(s)for Part A G1, follows cell division G2, cell division M, duplication of DNA S, immediately precedes cell division All of the listed choices are correctly matched.

replication of the DNA

Which of the following events occurs during interphase of the cell cycle? replication of the DNA separation of the spindle poles spindle formation condensation of the chromosomes

repeated mitosis without cytokinesis

Which of the following events would be most likely to produce cells with several nuclei? repeated mitosis without cytokinesis repeated mitosis with simultaneous cytokinesis multiple S phases without mitosis repeated cytokinesis without mitosis

replication of the DNA

Which of the following occurs during S phase? separation of sister chromatids spindle formation replication of the DNA condensation of the chromosomes

duplicated chromosomes attach to the plasma membrane

Which of the following occurs in binary fission but not in mitosis with cytokinesis? View Available Hint(s)for Part A replicated strands of DNA separate following the process, a membrane separates the two copies duplicated chromosomes attach to the plasma membrane replication of DNA begins at an origin the result produces two nuclei

A Cdk is an enzyme that attaches phosphate groups to other proteins.

Which of the following properties is associated with a cyclin-dependent kinase (Cdk)? A Cdk is an enzyme that attaches phosphate groups to other proteins. The number of Cdk molecules increases during the S and G2 phases and decrease during M. A Cdk is inactive, or "turned off," in the presence of a cyclin. A Cdk is an enzyme that catalyzes the attachment of kinetochores to microtubules.

The cells show characteristics of tumors.

Which of the following statements best describes cells in culture that do not exhibit either density-dependent inhibition or anchorage dependence? The cells have nonfunctional MPF. The cells follow an altered series of cell cycle phases. The cells show characteristics of tumors. The cells are unable to form spindle microtubules.

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

Which of the following statements best describes how cytokinesis differs between plant and animal cells? Plant cells deposit vesicles containing cell wall building blocks on the metaphase plate; animal cells form a cleavage furrow. Cytokinesis occurs between metaphase and anaphase in plant cells; it occurs after anaphase in animal cells. The contractile filaments found in plant cells are structures composed of carbohydrates; the cleavage furrow in animal cells is composed of contractile proteins. The structural proteins of plant cells separate the two cells; in animal cells, a cell membrane separates the two daughter cells.

They have entered into G0. Submit

Which of the following statements best explains how neurons and some other specialized cells divide infrequently? They can no longer degrade cyclins. They no longer produce MPF. They no longer have active nuclei. They have entered into G0.

alignment of chromosomes on the equator of the cell

Which of the following statements describes a characteristic feature of metaphase? alignment of chromosomes on the equator of the cell separation of the centromeres separation of sister chromatids cytokinesis

They are sites at which microtubules attach to chromosomes.

Which of the following statements describing kinetochores is correct? View Available Hint(s)for Part A They are located at the center of the centrosome; their function is to organize tubulin into elongated bundles called spindle fibers They interdigitate at the cell's equator and then move apart, causing the cell to elongate. They are the primary centromere structures that maintain the attachment of the sister chromatids prior to mitosis. 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. They are sites at which microtubules attach to chromosomes.

ATP as an energy source

Which of the following structures or molecules is required in order for motor proteins to facilitate movement of chromosomes toward the poles in mitosis? intact centromeres ATP as an energy source intact cohesin actin microfilaments

they need both if they are reproducing sexually Submit

Why do some species employ both mitosis and meiosis, whereas other species use only mitosis? View Available Hint(s)for Part A if they produce egg cells they do not require mitosis they need meiosis if the cells are producing organs such as ovaries if they produce large numbers of sperm cells they do not require meiosis a single-celled organism only needs mitosis they need both if they are reproducing sexually

interphase chromosomes are long, thin strands unlike the condensed chromosomes visible in mitosis Submit

Why is it difficult to observe individual chromosomes with a light microscope during interphase? View Available Hint(s)for Part A sister chromatids do not pair up until division starts the spindle must move them to the metaphase plate before they become visible the DNA has not been replicated yet they leave the nucleus and are dispersed to other parts of the cell interphase chromosomes are long, thin strands unlike the condensed chromosomes visible in mitosis