BIO181 Chapter 12 MasteringBiology Homework

Part E Spindle fibers attach to kinetochores during _____.

prometaphase

Part J Click on the art to see an animation. This animation illustrates the events of _____.

prometaphase

Part C Chromosomes become visible during _____.

prophase

Part H Click on the art to see an animation. This animation illustrates the events of _____.

prophase

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

suffering from cervical cancer

Part B Cytokinesis often, but not always, accompanies _____.

telophase

Part L Click on the art to see an animation. This animation illustrates the events of _____.

telophase

Part F - Evaluation

5 to 6

Part B - Phases of the cell cycle 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.

A) Non- dividing cells exit cell cycle B) At this point, cell commits to go through the cell cycle C) DNA replicates D) Centrosome replicates E) Mitotic spindle begins to from F) Cell divides, forming two daughter cells

Part B _____ is a carcinogen that promotes colon cancer.

fat

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

microwaves and cellphones

Part B - Mechanisms underlying the events of mitosis 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.

- Prophase: Tubulins assemble into spindle microtubules Cohesions join sister chromatids of duplicated chromosomes. - Prometaphase: Microtubules attach to kinetochores. - Metaphase: Kinetochores are motionless in relation to poles of cell - Anaphase: Cohesions break down Kinetochores move toward poles of the cell -Telophase: Spindle microtubules disassemble

Part B - Cytokinesis in plant cells 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.

- 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.

Part A - Comparing chromosome separation in bacteria and eukaryotes 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.

- eukaryotes only: Before separation, duplicated chromosomes condense. Nuclear envelope fragments, permitting chromosome separation. Two copies of the duplicated chromosome are attached at their centromeres before separating. - bacteria only: Chromosome separation begins at the origin of replication of DNA. - both: Chromosomes replicate before cell division. Replicated chromosomes separate by attaching to some other structural feature of the cell.

Part C - The roles of proteins in bacterial cell division and eukaryotic cytokinesis For each space in the table, drag the appropriate label to indicate if the statement is true or false for each group of organisms.

1. Cells divide by constriction of a ring of protein - bacteria: TRUE - animals: TRUE - plants: FALSE 2. The presence of a cell wall prevents the cell from dividing by constriction - bacteria: FALSE - animals: FALSE - plants: TRUE 3. Tubulin or tubulin-like molecules function in binary fission (in bacteria) or cytokinesis (in animals and plants). - bacteria: TRUE - animals: FALSE - plants: TRUE

Part A - Mitosis and cell cycle terminology 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.

1. DNA replication produces two identical DNA molecules, called sister chromatid(s), which separate during mitosis. 2.After chromosomes condense, the centromere(s) is the region where the identical DNA molecules are most tightly attached to each other. 3. During mitosis, microtubules attach to chromosomes at the kinetochore(s) 4. In dividing cells, most of the cell's growth occurs during interphase 5. The mitotic spindle(s) is a cell structure consisting of microtubules, which forms during early mitosis and plays a role in cell division. 6. During interphase, most of the nucleus is filled with a complex of DNA and protein in a dispersed form called chromatin. 7. In most eukaryotes, division of the nucleus is followed by cytokinesis, when the rest of the cell divides. 8. The centrosome(s) are the organizing centers for microtubules involved in separating chromosomes during mitosis.

Part D - Roles of the mitotic spindle Consider three questions concerning the animal cell that has been treated with the inhibitor. Drag the terms to answer the questions. Terms may be used once, more than once, or not at all.

1. Yes 2. Yes 3. No

Part C - The mitotic spindle 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 terms to the appropriate locations. Terms may be used once, more than once, or not at all.

1. lengthen 2. lengthen / shorten 3. disassemble

Part C - Changes in DNA structure during the cell cycle 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.

1. yes, yes, yes, no 2. no, no, yes, yes 3. yes, yes, yes, yes

Part D Which of the following is true?

Cancer-causing substances work in many different ways.

Part B 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.

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

DNA

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

E

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

G1

Part C 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.

Part B - Authority What is the affiliation of the writer?

The author is a medical doctor who serves leadership roles for cancer research and prevention organizations.

Part D - Reliability How can you know if the information is based on scientifically collected data and if it's corroborated by other sources? Scroll to the end of the article, and skim the references provided. What do you find in the References list at the bottom of the page?

The references are all from primary sources.

Part D 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.

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

They need both if they are producing animal gametes.

Part A Which of the following is true of benign tumors, but not malignant tumors? - They are the result of the transformation of normal cells. - They remain confined to their original site - They have an unusual number of chromosomes. - They migrate from the initial site of transformation to other organs or tissues. - They can divide indefinitely if an adequate supply of nutrients is available.

They remain confined to their original site

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

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

Part E Now, search for information on the risks of UV exposure and skin cancer on at least two other web sites, including MedlinePlus (nlm.nih.gov) and the American Cancer Society (cancer.org). Is the information provided by these sites consistent with what you found on the Skin Cancer Foundation web site?

Yes, other sites corroborate the information on the Skin Cancer Foundation site.

Part A - Identifying the stages of mitosis 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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Part A - First impression On a scale of 0 to 6, where 6 is the most trustworthy, how would you rate this site? (Note that all responses will be marked as "correct" at this point.)

[the answer doesn't matter]

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

all of the above

Part A Which of these is NOT a carcinogen?

all of the above are carcinogens

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

anaphase

Part F Click on the art to see an animation. This animation illustrates the events of _____.

anaphase

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

carcinogen

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

cleavage

Part G Click on the art to see an animation. This animation illustrates the events of _____.

cytokinesis as it occurs in animal cells

Part K Click on the art to see an animation. This animation illustrates the events of _____.

cytokinesis as it occurs in plant cells

Part A Nucleoli are present during _____.

interphase

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

interphase

Part I Click on the art to see an animation. This animation illustrates the events of _____.

metaphase

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

the mitotic phase

Part C - Motivation Next, can you identify what the source is trying to accomplish by providing this information? As you read the article, think about what the writer's agenda might be with regard to indoor tanning. What seems to be the main purpose of the article?

to summarize the data demonstrating the carcinogenic effects of UV radiation from indoor tanning

Part M During prophase a homologous pair of chromosomes consists of _____.

two chromosomes and four chromatids