Ch. 12 Q's

What does MPF stand for?

"maturation-promoting factor" or ""M-phase-promoting factor"

What do multicellular organisms need cell division for?

- development of fertilized egg - growth - repair

How many sets of chromosomes do gametes in animals have?

1

What does each euk. chromosome consist of?

1 DNA molecule associated with many proteins = Chromatin

What are the two main things that euk. cell division consists of?

1. Mitosis 2. Cytokinesis

What two things make up the mitotic (M) phase of the cell cycle?

1. Mitosis 2. Cytokinesis

In which of the three phases of interphase and the stages of mitosis do chromosomes exist as single DNA molecules?

?

How does a cell grow throughout all three phases of interphase?

By producing proteins & cytoplasmic organelles such as mitochondria and ER.

*During which stage of the cell cycle do sister chromatids separate?* a. anaphase b. metaphase c. G2 phase d. prophase e. G1 phase

a. anaphase

*The phase of mitosis during which the chromosomes move toward separate poles of the cell is __________.* a. anaphase b. prophase c. prometaphase d. metaphase e. telophase

a. anaphase Anaphase begins when the cohesins joining sister chromatids are cleaved, allowing the chromatids (now called 'chromosomes') to move toward opposite poles of the cell.

*At which stage of mitosis are chromosomes lined up in one plane in preparation for their separation to opposite poles of the cell?* a. metaphase b. prophase c. anaphase d. interphase e. telophase

a. metaphase

*During what phase in the cell cycle would you find the most DNA per cell?* a. S₁ b. G₂ c. G₀ d. G₁ e. S

b. G₂

*Which of the following does not occur during mitosis?* a. condensation of the chromosomes b. spindle formation c. separation of the spindle poles d. replication of the DNA e. separation of sister chromatids

d. replication of the DNA

How many sets of chromosomes do somatic cells in animals have?

2

What is the difference in how animal and plant cells carry out cytokinesis?

Animals: Use cleavage Plants: Form a cell plate

How many chromosomes are shown in the illustration in F.12.8? Are they duplicated? How many chromatids are shown?

Chromosomes: 12? Yes they are duplicated? Chromatins: 6?

What follows mitosis?

Cytokinesis

What are intermediate filaments made of?

Fibrous proteins coiled into cables.

What do microfilaments do?

Function in muscle contraction and changes in cell shape.

What are microtubules made of?

Hollow rods constructed from globular proteins called tubulins.

Where do important checkpoints occur?

In the G₁, G₂, and M phases

What do intermediate filaments do?

Maintain cell shape and anchor the nucleus.

What do unicellular organisms need cell division for?

Reproduction

What do microtubules do?

Shape and support the cell and serve as tracks along which organelles equipped with motor proteins can move.

What are microfilaments made of?

Subunits of actin.

Why can't proteins pass through the cell membrane?

The hydrophobic interior of the membrane impedes direct passage of proteins into the cell.

*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. Benign tumors do not arise by transformation; malignant tumors do. c. Cells of benign tumors metastasize; those of malignant tumors do not. d. Benign tumors arise by transformation; malignant tumors do not. e. Benign tumors will not kill you; malignant tumors will.

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

*Which of the following hypotheses is best supported by observing cancer cells in a culture? * a. The cancer cells do not exhibit density-dependent inhibition. b. The cancer cells exhibit anchorage dependence. c. The cancer cells produce molecules that inhibit the growth factors required for cell division. d. The cancer cells spend the majority of their time in the G0 phase. e. All of the listed responses are correct.

a. The 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.

*Which of the following is a hallmark of cancer cells?* a. They multiply quickly. b. They die quickly. c. There is no limit to their size. d. They ingest other cells.

a. They multiply quickly.

*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?* a. 50 units b. 100 units c. between 50 and 100 units d. 200 units e. 400 units

b. 100 units Recall that G2 follows S and that during the S phase, DNA is replicated.

*If a human somatic cell is just about to divide, it has __________ chromatids.* a. 0 b. 23 c. 46 d. 92 e. There is insufficient information to answer the question.

d. 92 Human somatic cells have 92 chromatids just prior to cell division due to the replication of the 46 chromosomes that occurred during the S phase.

*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?* a. 23 b. 46 c. 92 d. 94 e. 98

d. 94 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.

*The region of a chromosome in which the two double strands of replicated DNA are held together is called __________.* a. an aster b. chromatin c. a centriole d. a centromere e. a chromatid

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

*Which event or events occur during anaphase?* a. A spindle made of microtubules is present during anaphase. b. The centrioles are at opposite poles during anaphase. c. Cohesins joining sister chromatids at the centromeres are cleaved during anaphase. d. Genetically identical chromosomes (previously sister chromatids) move to opposite poles during anaphase. e. All of the listed responses are correct.

e. All of the listed responses are correct. Anaphase begins when the cohesins connecting sister chromatids are cleaved, liberating the chromatids (now called chromosomes), which begin moving toward opposite poles of the cell.

*DNA replication occurs in __________.* a. cytokinesis b. prophase of mitosis c. metaphase of mitosis d. the G1 phase of interphase e. the S phase of interphase

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

*Which of the following processes does NOT occur in dividing bacteria?* a. replication of DNA b. binary fission c. separation of the origins of replication d. inward growth of the plasma membrane e. mitosis

e. mitosis 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.

*A cell entering the cell cycle with 32 chromosomes will produce two daughter cells, each with __________.* a. 16 chromosomes b. 64 chromosomes c. 32 pairs of chromosomes d. 64 pairs of chromosomes e. none of the listed numbers of chromosomes

e. none of the listed numbers of chromosomes There would be 32 chromosomes present in each of the daughter cells.

*The centromere is a region in which __________.* a. the chromosomes are connected to the cell plate in metaphase b. chromosomes become aligned during metaphase c. the new cell plate forms in telophase d. microtubules are fastened to the centrioles during anaphase e. sister chromatids are attached to one another in prophase

e. sister chromatids are attached to one another in prophase

During which stages of the cell cycle does a chromosome consist of 2 identical chromatids?

The 2nd & 3rd stages of cell division?

*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. 0 b. 7 c. 14 d. 28 e. None of the listed responses is correct.

a. 0 By telophase, the chromatids have separated and the individual units of DNA (now called chromosomes) are arriving at the poles. There are no chromatids at this point.

*How many maternal chromosomes are present in a somatic human cell not engaged in cell division?* a. 23 b. 46 c. 92 d. 184 e. None of the listed responses is correct.

a. 23 Human somatic cells contain a total of 46 chromosomes, half of which are maternally derived.

*A human bone marrow cell, in prophase of mitosis, contains 46 chromosomes. How many chromatids does it contain?* a. 92 b. 23 c. 46 d. 46 or 92, depending on the portion of prophase examined e. 23 or 46, depending on the portion of prophase examined

a. 92 Mitosis follows the duplication of the cell's DNA.

*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 the G1 and G2 phases b. between the G2 phase and prophase c. during the M phase of the cell cycle d. between anaphase and telophase e. between prophase and anaphase

a. between the G1 and G2 phases Between these two phases of the cell cycle, the DNA is replicated during the S 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?* a. large cells containing many nuclei b. a rapid rate of gamete production c. a decrease in chromosome number d. division of the organism into many cells, most lacking nuclei e. inability to duplicate DNA

a. large cells containing many nuclei

*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?* a. 15 b. 30 c. 45 d. 60 e. 120

b. 30 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.

*Which of the following is involved in the binary fission of most bacteria?* a. prophase, prometaphase, metaphase, anaphase, and telophase b. distribution of a copy of the single parental chromosome to each daughter cell c. disintegration of the nuclear membrane d. formation of a cell plate e. formation of a spindle apparatus

b. distribution of a copy of the single parental chromosome to each daughter cell Prokaryotes reproduce by a type of cell division called binary fission, which involves replicating the single chromosome and distributing the copies equally to two daughter cells.

*During _____ the cell grows and replicates both its organelles and its chromosomes.* a. S b. interphase c. mitosis d. cytokinesis e. G1

b. interphase

*One event occurring during prophase is __________.* a. the alignment of chromosomes in a single plane b. the beginning of the formation of a spindle apparatus c. the synthesis of a new nuclear envelope d. the division of the centromere e. cytokinesis

b. the beginning of the formation of a spindle apparatus

*Which of the following is FALSE regarding sister chromatids?* a. Sister chromatids are separated during mitosis. b. Sister chromatids are created when DNA is replicated. c. Both of the sister chromatids end up in the same daughter cell after cytokinesis has occurred. d. Sister chromatids form in the S-phase stage of the cell cycle. e. Sister chromatids are attached to one another at the centromere.

c. Both of the sister chromatids end up in the same daughter cell after cytokinesis has occurred. Each of the sisters ends up in a different cell after cell division.

*When a cell in S phase is fused with a cell in G1, __________.* a. the replication of DNA occurring in the original S nucleus is terminated b. the two nuclei fuse and additional division is arrested c. DNA synthesis begins immediately in the original G1 nucleus d. the original G1 cell will divide immediately e. the chromosomes of the original G1 nucleus condense in preparation for mitosis

c. DNA synthesis begins immediately in the original G1 nucleus This observation indicates that cytoplasmic signals can participate in the regulation of the cell cycle.

*Cell A has half as much DNA as cells B, C, and D in a mitotically active tissue. Cell A is most likely in* a. prophase. b. metaphase. c. G1. d. G2.

c. G1.

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

c. G1: follows cell division After mitosis and cytokinesis, the newly formed daughter cells enter the G1 phase.

*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?* a. spindle formation b. spindle attachment to kinetochores c. cleavage furrow formation and cytokinesis d. cell elongation during anaphase e. DNA synthesis

c. cleavage furrow formation and cytokinesis

*In animal cell mitosis, the cleavage furrow forms during which stage of the cell cycle?* a. the G1 phase b. anaphase c. cytokinesis d. prophase e. metaphase

c. cytokinesis Cytokinesis is usually well under way by telophase. In animal cells, cytokinesis involves the formation of a cleavage furrow, which pinches the cell in two.

*During interphase, the genetic material of a typical eukaryotic cell is __________.* a. condensed and the chromosomes are often visible under the light microscope b. attached to microtubule spindle fibers c. dispersed in the nucleus as long strands of chromatin d. transported through the nuclear pores e. dispersed in the cytoplasm as long strands of chromatin

c. dispersed in the nucleus as long strands of chromatin During interphase, the chromosomes cannot be distinguished individually because the chromosomes are still in the form of loosely packed chromatin fibers.

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

c. disruption of mitotic spindle formation.

*Which of the following represents a mismatch or incorrect description?* a. prophase: chromosomes become more tightly coiled b. anaphase: there is movement of the chromosomes to the poles c. metaphase: the nuclear envelope disappears d. telophase: chromosomes become more extended e. metaphase: chromosomes line up on the equatorial plane

c. metaphase: the nuclear envelope disappears During prometaphase, the nuclear envelope fragments.

*In a human skin cell that is going through the cell cycle, when do the centrosomes separate?* a. metaphase b. G2 phase c. prophase d. S phase e. anaphase

c. prophase The centrosomes move away from each other during prophase, apparently propelled along the surface of the nucleus by the lengthening bundles of microtubules between them.

*Which of the following does NOT occur during mitosis?* a. separation of chromatids b. condensation of chromatin c. replication of chromosomes d. the movement of chromosomes to opposite poles e. alignment of chromosomes along the cell's equator

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

*Which of the following phases of mitosis is essentially the OPPOSITE of prometaphase in terms of the nuclear envelope?* a. anaphase b. S phase c. telophase d. metaphase e. interphase

c. telophase 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.

*The decline of MPF activity at the end of mitosis is due to* a. the accumulation of cyclin. b. synthesis of DNA. c. the degradation of cyclin. d. the destruction of the protein kinase Cdk. e. decreased synthesis of Cdk.

c. the degradation of cyclin.

*During _____ both the contents of the nucleus and the cytoplasm are divided.* a. G1 b. mitosis c. the mitotic phase d. G2 e. S

c. the mitotic phase The mitotic phase encompasses both mitosis and cytokinesis.

*Following cytokinesis in an animal cell, how many centrioles does each new daughter cell possess?* a. zero b. one c. two d. four e. eight

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

*Which of the following statements best describes microtubules?* a. Microtubules are fibrous proteins coiled into cables that maintain cell shape and anchor the nucleus. b. Microtubules are made up of subunits of actin, and function in muscle contraction and changes in cell shape. c. Microtubules are permanent cellular structures that help the cell to move from place to place. d. Microtubules are made up of subunits of tubulin, and are structures along which substances are transported in the cell.

d. Microtubules are made up of subunits of tubulin, and are structures along which substances are transported in the cell. Microtubules—hollow rods constructed from globular proteins called tubulins—shape and support the cell and serve as tracks along which organelles equipped with motor proteins can move. Microfilaments are made up of subunits of actin, and function in muscle contraction and changes in cell shape. Intermediate filaments are fibrous proteins coiled into cables that maintain cell shape and anchor the nucleus.

*Which of the following is true of kinetochores?* a. They are the primary centromere structures that maintain the attachment of the sister chromatids prior to mitosis. 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 located at the center of the centrosome; their function is to organize tubulin into elongated bundles called spindle fibers. d. They interdigitate at the cell's equator and then move apart, causing the cell to elongate. e. They are sites at which microtubules attach to chromosomes.

e. 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.

*Chromatids are __________.* a. the bacterial equivalent of eukaryotic chromosomes b. found only in aberrant chromosomes c. held together by the centrioles d. composed of RNA e. identical copies of each other if they are part of the same duplicated chromosome

e. identical copies of each other if they are part of the same duplicated chromosome Each duplicated chromosome consists of two identical sister chromatids.

How many chromosomes are drawn in each part of F.12.5?

2 chromosomes are drawn together?

Differentiate between these terms: chromosomes, chromatin, and chromatid

Chromosomes: cellular structure made of 1 DNA molecule + associated protein molecules Chromatin: A complex of chromosomes Chromatid: Copies of duplicated chromosomes?

What are the key molecules of the cell cycle control system?

Cyclins & Cyclin-Dependent Kinases (Cdks)

*What effect does phosphorylating a protein have on that protein?* a. Phosphorylation adds one or more phosphorus atoms to the protein, allowing it to perform a particular function. b. Phosphorylation adds energy to the protein, allowing it to form ATP from ADP and Pi. c. Phosphorylation may have no effect at all on the protein. d. Phosphorylation changes the shape of the protein, most often activating it.

d. Phosphorylation changes the shape of the protein, most often activating it. Protein phosphorylation causes a shape change in the phosphorylated protein. The shape change results from the interaction of the newly added phosphate groups with charged or polar amino acids on the protein being phosphorylated. The shape change alters the function of the protein, most often activating it, but in some cases phosphorylation instead decreases the activity of the protein.

*In the cells of some organisms, mitosis occurs without cytokinesis. This will result in* a. cell cycles lacking an S phase. b. cells that are unusually small. c. destruction of chromosomes. d. cells with more than one nucleus. e. cells lacking nuclei.

d. cells with more than one nucleus.

*Tissue culture experiments with PDGF demonstrate that without this substance __________.* a. cells divide in an uncontrolled fashion, confirming PDGF's role as a cell division inhibitor b. bacterial cells lose their resistance to antibiotics c. the various kinases, such as MPF, are unable to bind to cyclin d. fibroblasts fail to divide e. animal cells are unable to attach to the substratum

d. fibroblasts fail to divide PDGF is a specific growth factor for fibroblasts.

*You would be UNLIKELY to see which of the following human cells dividing?* a. cell from an embryo b. cancer cell c. skin cell d. nerve cell e. All of these cell types are equally unlikely to divide at any given time.

d. nerve cell Nerve cells are quite complex and specialized. After reaching maturity, they enter the G0 phase.

*In telophase of mitosis, the mitotic spindle breaks down and the chromatin uncoils. This is essentially the opposite of what happens in __________.* a. metaphase b. S phase c. anaphase d. prophase e. interphase

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

*"Cytokinesis" refers to __________.* a. the reduction in the number of chromosomes b. the division of the nucleus c. the movement of a cell from one place to another d. the division of the cytoplasm e. the division of the entire cell

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

*During binary fission in a bacterium, __________.* a. the two DNA molecules divide in half, forming four DNA fragments b. the two DNA molecules break up into plasmids c. the two DNA molecules float free in the cell and are guided to daughter cells by a spindle-like apparatus d. the origins of replication move apart e. the two DNA molecules attach to the centrioles

d. the origins of replication move apart This occurs during binary fission.