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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

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a plant cell in the process of cytokinesis.

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Vinblastine is a standard chemotherapeutic drug used to treat cancer. Because it interferes with the assembly of micro-tubules, its effectiveness must be related to

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disruption of mitotic spindle formation.

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

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continue to divide even when they are tightly packed together.

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

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the degradation of cyclin.

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In the cells of some organisms, mitosis occurs without cytoki-nesis. This will result in

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cells with more than one nucleus.

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Which of the following does not occur during mitosis?

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replication of the DNA

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What is true of all cancers?

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They have escaped normal cell cycle controls.

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How do cancer cells differ from normal cells?

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Cancer cells may be immortal.

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The cell cycle control systems of cancer cells differ from those of normal cells. Select the best explanation for this fact.

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Genetic changes alter the function of the cancer cell's protein products.

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If a eukaryotic cell is in the G1 phase of the cell cycle, which statement about the cell's chromosomes must be correct?

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Each chromosome is made of a complex of DNA and associated proteins.

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Which statement provides the best description of the interphase portion of the cell cycle?

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During interphase, a cell is metabolically active.

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An environmental substance that is known to cause cancer is called a what?

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carcinogen

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Radiation emitted from which of the following two sources are most alike?

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microwaves and cellphones

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You are trying to discover if the pesticide atrazine is a mutagen. Where are you looking for mutations?

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DNA

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Which of the following is true?

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Cancer-causing substances work in many different ways.

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Which of the following best summarizes current scientific opinion regarding cellphones and brain cancer?

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While most studies indicate that cellphones do not cause brain cancer, more research needs to be done as cellphone use increases.

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Which of the following codes for proteins?

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genes

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You are developing a new drug that damages the cells that provide the supportive structure required by a tumor. Which type of cell are you targeting?

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fibroblast

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A tumor would not be able to have its own blood supply if it weren't for which of the following?

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endothelial cells immune system cells

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Which of the following appears to be true according to current research?

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As the population of Helicobacter pylori decreases in the human body, cases of esophageal cancer increase.

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Can you match these prefixes, suffixes, and word roots with their definitions?

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single: haplo both, double: diplo- same: homo- (or homeo-) without, lack of, not: a- (or an-) small: micro- to produce: -gen- body: -some (or soma-) chromosomes: ploid color: chrom- self: auto- many: multi- end: telo- before: pro- two: bi- one: uni- between: inter- segment, body section: -mere thread: mito- cell: -cyte (or cyto-) moving: kin- (or kinet-)

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Prior to this new technique, how were mice given cancerous tumors?

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The tumors were implanted under the skin.

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You are an oncologist. A patient presents with advanced prostate cancer and you follow standard protocol. What do you do?

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The patient is treated with chemical castration.

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You are an endocrinologist studying new treatments for prostate cancer. You have a patient with an unusually large level of dihydrotestosterone. Which of the following is true?

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Your patient's cancer has become resistant to the standard treatment.

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Which of the following is true regarding prostate cancer cells?

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They can activate and inactivate certain genes.

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Your uncle has prostate cancer. Which of the following indicates improvement in his condition?

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A decreasing PSA.

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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

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G1

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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?

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cleavage furrow formation and cytokinesis

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Which of the following is a large reason behind the increase in breast cancer in developing countries?

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Women are living longer.

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Which of the following is true?

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Worldwide, breast cancer is the most common cancer in women, and the largest cancer killer of women.

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You are an oncologist specializing in colon cancer. A patient presents to you with disease that has spread to his bones and liver and there is no treatment available. What stage cancer is this?

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4

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A woman in Uganda is diagnosed with breast cancer. If any treatment is done, what is it most likely to be?

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Only a mastectomy.

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You are a breast cancer survivor and advocate in the U.S. Why do you promote self breast exams to women under 50 rather than annual mammograms?

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Women under 50 tend to have denser breast tissue which often make mammograms inconclusive.

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

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They need both if they are producing animal gametes.

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

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92

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

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They have uncoiled to form long, thin strands.

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In eukaryotic cells, chromosomes are composed of _____.

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DNA and proteins

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What is the final result of mitosis in a human?

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genetically identical somatic cells containing 46 chromosomes

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Starting with a fertilized egg (zygote), a series of five cell divisions would produce an early embryo with how many cells?

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32

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If there are 20 duplicated chromosomes in a cell, how many centromeres are there?

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20

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As in most areas of biology, the study of mitosis and the cell cycle involves a lot of new terminology. Knowing what the different terms mean is essential to understanding and describing the processes occurring in the cell. Drag the terms on the left to correctly complete these sentences. Not all the terms will be used.

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sister chromatid(s) centromere(s) kinetocchore(s) interphase mitotic spindle (s) chromatin cytokinesis centrosome (s)

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The cell cycle represents the coordinated sequence of events in the life of a cell from its formation to its division into two daughter cells. Most of the key events of the cell cycle are restricted to a specific time within the cycle. In this exercise, you will identify when various events occur during the cell cycle. Recall that interphase consists of the G1, S, and G2 subphases, and that the M phase consists of mitosis and cytokinesis. Drag each label to the appropriate target.

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*Many organisms contain cells that do not normally divide. These cells exit the cell cycle before the G1 checkpoint. Once a cell passes the G1 checkpoint, it usually completes the cell cycle--that is, it divides. The first step in preparing for division is to replicate the cell's DNA in the S phase. In the G2 phase, the centrosome replicates. In early M phase, the centrosomes move away from each other toward the poles of the cell, in the process organizing the formation of the mitotic spindle. At the end of the M phase when mitosis is complete, the cell divides (cytokinesis), forming two genetically identical daughter cells.

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As the chromosomes of a parent cell are duplicated and distributed to the two daughter cells during cell division, the structure of the chromosomes changes. Answer the three questions for each phase of the cell cycle by dragging the yes and no labels to the appropriate locations in the table. Note: Assume that by the end of the M phase, the parent cell has not yet divided to form two daughter cells.

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Sister chromatids form when DNA replicates in the S phase. The sister chromatids become individual chromosomes once they separate in early anaphase. Similarly, the cellular DNA content doubles in the S phase when the DNA replicates. However, the cell's DNA content does not return to its normal (undoubled) levels until after cytokinesis is complete and two daughter cells have formed. The condensation state of the DNA is not related to the presence or absence of sister chromatids. The DNA condenses in prophase and remains condensed until after the sister chromatids separate and the new daughter cells begin to form. In late telophase/cytokinesis, the emphasis shifts to cell growth and DNA replication for the next cell cycle. For these processes to occur, the DNA needs to be de-condensed so it is accessible to the cellular machinery involved in transcription.

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The stages of mitosis were originally defined by cellular features observable through a light microscope. The six micrographs below show animal cells (lung cells from a newt) during the five stages of mitosis, plus cytokinesis. (Note that interphase is not represented in these micrographs.) In these images, the chromosomes have been stained blue, microtubules green, and microfilaments red. Drag each micrograph to the target that indicates the stage of mitosis or cytokinesis it shows.

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*As these six micrographs demonstrate, cellular events observable by light microscopy can be used to define the six stages of mitosis and cytokinesis. However, deciphering which stage is which in real cells can be much more challenging than in the drawings of idealized cells you see in your textbook. Thus, it is important to carefully observe the completeness of the mitotic spindle and the location of the chromosomes, as well as how condensed the chromosomes are.

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Mitosis unfolds through a sequence of stages marked by specific events in the cell. The structural changes in the cell are brought about by a series of tightly coordinated underlying mechanisms. Sort each process into the appropriate bin to indicate the stage of mitosis in which it occurs. If a process occurs in more than one stage, sort it to the stage when it first occurs.

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*The micrographs in Part A show some of the cellular processes that occur during the stages of mitosis. In prophase, the microtubules of the spindle apparatus begin to assemble from individual tubulin subunits. As the identical chromatids of each pair of sister chromatids condense during this stage, they are held together by cohesin proteins. Prometaphase is marked by fragmentation of the nuclear envelope, expansion of the spindle into the nuclear region, and attachment of some spindle fibers to the chromosomes via the kinetochores. Metaphase, marked by the alignment of chromsomes along the metaphase plate, is brought about by kinetochores aligning and then remaining motionless relative to the poles of the cell. In anaphase, the cohesin proteins are cleaved, and the kinetochores move toward the poles of the cell, separating the sister chromatids. As telophase proceeds, the kinetochore microtubules of the spindle disassemble. As the chromosomes reach the poles of the cell, the nuclear envelopes of the two new daughter nuclei form.

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The mitotic spindle consists of two types of microtubules: kinetochore microtubules and nonkinetochore microtubules. In animal cells, these two types of microtubules function differently in the stages of mitosis. Complete the sentences by dragging the labels to the appropriate locations. Labels may be used once, more than once, or not at all.

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lengthen lengthen; shorten disassemble

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Consider three questions concerning the animal cell that has been treated with the inhibitor. Drag the labels to answer the questions. Labels may be used once, more than once, or not at all.

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y y n

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In all cells, separation of replicated chromosomes is a prerequisite for cell division. However, the mechanism of chromosome separation in bacteria is distinct from that in eukaryotes in several ways. Sort the following statements into the appropriate bin.

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*Although the processes of chromosome separation in bacteria and eukaryotes have a common evolutionary origin, the actual mechanisms are different. Structurally, bacterial cells contain a single chromosome that is much shorter than those in eukaryotic cells, and bacterial cells lack a mitotic spindle. The bacterial chromosome does not fully condense before separation. However, the physical separation of the replicated bacterial chromosomes still involves attachment to some structure in the cell: possibly the plasma membrane at the origins of replication.

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Cytokinesis in animal cells is accomplished by constriction of the cell along the plane of cell division (formation of a cleavage furrow). In plant cells, which have cell walls, a completely different mechanism of cytokinesis has evolved. Which of the following statements are true of cytokinesis in plant cells? Select the two that apply.

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The cell plate consists of the plasma membrane and cell wall that will eventually separate the two daughter cells. Vesicles from the Golgi apparatus move along microtubules, coalesce at the plane of cell division, and form a cell plate.

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Plant and animal cells also require cytoskeletal proteins for cytokinesis, although the roles these proteins play differ among bacteria, plants, and animals. For each space in the table, drag the appropriate label to indicate if the statement is true or false for each group of organisms.

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true; true; false false; false; true true; false; true

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Which of these phases encompasses all of the stages of mitosis but no other events?

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E

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

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the mitotic phase

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

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interphase

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Nucleoli are present during _____.

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interphase

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Cytokinesis often, but not always, accompanies _____.

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telophase

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Chromosomes become visible during _____.

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prophase

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

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anaphase

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Spindle fibers attach to kinetochores during _____.

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prometaphase

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