FINAL 07 2020, questions and answers PDF

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Module_7_ Ch_12...

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6/13/2020

Module #7: Ch 12

Module #7: Ch 12 Due: 11:59pm on Thursday, July 1, 2021 You will receive no credit for items you complete after the assignment is due. Grading Policy

Activity: Mitosis and Cytokinesis Animation

Click here to complete this activity. Then answer the questions.

Part A Nucleoli are present during _____. ANSWER:

interphase anaphase prophase metaphase prometaphase

Correct Nucleoli are present during interphase.

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

telophase metaphase prometaphase anaphase interphase

Correct Cytokinesis often, but not always, accompanies telophase.

Part C Chromosomes become visible during _____. ANSWER:

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Module #7: Ch 12 anaphase interphase prophase metaphase prometaphase

Correct During prophase, the chromatin fibers become discrete chromosomes.

Part D Centromeres divide and sister chromatids become full-fledged chromosomes during _____. ANSWER: anaphase prometaphase metaphase interphase telophase

Correct During anaphase, sister chromatids separate and daughter chromosomes migrate to opposite poles.

Part E Spindle fibers attach to kinetochores during _____. ANSWER: anaphase telophase metaphase interphase prometaphase

Correct Attachment of spindle fibers to kinetochores is one of the events of prometaphase.

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

ANSWER:

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Module #7: Ch 12 anaphase prophase interphase metaphase telophase

Correct During anaphase centromeres come apart, and sister chromatids become full-fledged chromosomes, which migrate to opposite poles of the cell.

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

ANSWER: cytokinesis as it occurs in animal cells prophase metaphase prometaphase cytokinesis as it occurs in plant cells

Correct Cytokinesis in animal cells involves the formation of a cleavage furrow.

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

ANSWER:

interphase anaphase telophase prometaphase prophase

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Correct Events of prophase include the condensation of chromatin and the dispersal of nucleoli.

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

ANSWER: telophase prometaphase anaphase metaphase prophase

Correct During metaphase chromosomes align along the metaphase plate.

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

ANSWER:

cytokinesis as it occurs in plant cells prometaphase interphase anaphase metaphase

Correct The events of prometaphase include the attachment of spindle fibers to kinetochores.

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

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Module #7: Ch 12

ANSWER:

anaphase prometaphase prophase cytokinesis as it occurs in plant cells metaphase

Correct Cytokinesis in plant cells involves the formation of a cell plate.

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

ANSWER: metaphase prometaphase anaphase prophase telophase

Correct During telophase both nuclear envelopes and nucleoli re-form.

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

two chromosomes and four chromatids two chromosomes and two chromatids four chromosomes and two chromatids one chromosome and four chromatids one chromosome and two chromatids

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Module #7: Ch 12

Correct At this point each of the chromosomes consists of two chromatids.

Activity: The Cell Cycle

Click here to complete this activity. Then answer the questions.

Part A Which of these phases encompasses all of the stages of mitosis?

ANSWER: D C E A B

Correct This is mitosis.

Part B During _____ both the contents of the nucleus and the cytoplasm are divided. ANSWER: S the mitotic phase G2 mitosis G1

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Correct The mitotic phase encompasses both mitosis and cytokinesis.

Part C During _____ the cell grows and replicates both its organelles and its chromosomes. ANSWER: cytokinesis mitosis interphase S G1

Correct These are the events of interphase.

Activity: Causes of Cancer

Click here to complete this activity. Then answer the questions.

Part A Which of these is NOT a carcinogen? ANSWER:

UV light testosterone fat cigarette smoke all of the above are carcinogens

Correct All of these substances can cause cancer.

Part B _____ is a carcinogen that promotes colon cancer. ANSWER:

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Module #7: Ch 12 fat UV light estrogen a virus testosterone

Correct A diet high in fat increases the risk of both colon and breast cancer.

Activity: Four Phases of the Cell Cycle

Click here to view this animation. Then answer the questions.

Part A Which of the following is a function of the S phase in the cell cycle?

Hint 1. What does the S in S phase represent?

ANSWER: The synchronization of organelle division The sorting of chromosomes The synthesis of sister chromatids The separation of sister chromatids

Correct DNA replication occurs during S phase and results in two sister chromatids for each original chromosome.

Part B The copying of chromosomes occurs during which of the following phases of the cell cycle?

Hint 1. Consider what each phase name stands for.

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ANSWER:

S phase G2 phase G1 phase M phase

Correct Chromosomes must undergo replication before mitosis can occur; this copying occurs during the S phase.

Part C For the first several divisions of early frog embryos, cells proceed directly from the M phase to the S phase and back to M without gaps. Which of the following is likely to be true about dividing cells in early frog embryos?

Hint 1. What normally occurs during gap phases?

ANSWER:

Frog embryos do not have DNA. The cells do not divide by mitosis. The number of chromosomes decreases with each generation. The cells get smaller with each generation.

Correct Without gap phases, the cells have no opportunity to grow.

Part D True or false? The M phase is characterized by the replication and division of a cell's chromosomes.

Hint 1. Cells prepare for DNA synthesis during the G1 phase.

ANSWER:

True False

Correct Correct: Cells replicate their chromosomes during the S phase and divide partition their chromosomes during the M phase.

Part E If an organism normally has 34 chromosomes, how many molecules of DNA should there be in the G1 phase of the cell cycle?

Hint 1.

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Module #7: Ch 12

Review the cell cycle, the timing of DNA replication, and the timing of segregation of chromosomes during mitosis.

ANSWER: 17 136 68 34

Correct There is one DNA molecule per chromosome.

Part F Which of the following events would cause the cell cycle to arrest?

Hint 1. Consider the assessments that must be made at each of the three checkpoints in the cell cycle.

ANSWER: Complete chromosome replication Poor nutrient conditions Synthesis of cyclins by growth factors and activation of a cyclin-Cdk complex Chromosomes lined up along the metaphase plate

Correct Poor nutrient conditions would arrest the cell cycle at the G1 checkpoint.

Mitosis (3 of 3): Comparing Cell Division in Animals, Plants, and Bacteria (BioFlix tutorial) The division of any cell, prokaryotic or eukaryotic, requires that the genetic information in each of the parent cell’s chromosomes be faithfully copied and distribute into each daughter cell. Only then does the cell physically divide. Because of their divergent evolutionary paths, bacteria, plants, and animals have somewhat different mechanisms of chromosome separation and cell division.

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.

Hint 1. Review of changes to chromosomes during cell division in eukaryotes In eukaryotic cells, replication of each chromosome is accompanied by complex changes in the structure of the chromosomes. These changes begin during S phase of interphase and result in the formation of a pair of fully condensed sister chromatids in prometaphase of mitosis. Watch this segment of the Mitosis animation to see these structural changes that occur in a eukaryotic cell.

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Module #7: Ch

Hint 2. What structures in bacterial cells are likely involved in chromosome separation? A bacterial cell contains a single, circular chromosome. As in a eukaryotic cell, after replication of the DNA, the chromosomes move to opposite ends of the bacterial cell prior to cell division by a mechanism that is not fully understood. In order for the chromosomes to separate, they must attach to something in the cell. Based on what is known about how bacterial chromosomes separate, which of the following structural features of a bacterial cell likely play a role in chromosome separation? Select the two that apply. ANSWER:

plasma membrane origin of replication (where DNA replication starts on the chromosome) nuclear envelope spindle microtubules

Hint 3. How do structural properties of bacterial chromosomes influence what happens to them during cell division? Although all chromosomes consist of DNA, bacterial chromosomes are structurally distinct from their eukaryotic cousins. How do these differences affect what happens to bacterial chromosomes during cell division? Which of the following statements are correct? Select the two that apply. ANSWER:

A bacterial chromosome is highly folded and coiled, but lacks the fully condensed structure of a eukaryotic chromosome during cell division. Following replication of the DNA, bacterial chromosomes remain physically associated with each other until just before cell division occurs. A bacterial chromosome consists of double-stranded DNA, and thus replication of the DNA before cell division is not necessary.

ANSWER:

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Before separation, duplicated chromosomes condense.

Chromosome separation begins at the origin of replication on DNA.

Nuclear envelope fragments, permitting chromosome separation. Two copies of the duplicated chromosome are attached at their centromeres before separating.

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Replicated chromosomes separate by attaching to some other structural feature of the cell. Chromosomes replicate before cell division.

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Correct 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.

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 hav 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.

Hint 1. Formation of the cell plate During cytokinesis in a plant cell, the cell plate forms as vesicles derived from the Golgi apparatus fuse along the plane of cell division. As more vesicles fuse with the cell plate, it grows outward until it fuses with the plasma membrane of the parent cell.

Hint 2. What role, if any, do either microtubules or microfilaments play in cytokinesis in plant cells? Both microtubules and microfilaments are parts of the cytoskeleton and are important in many cellular processes, including motion and determination of cell shape. Which of the following statements correctly describes the role of these cytoskeletal elements in plant cytokinesis? ANSWER:

Both microtubules and microfilaments move the cell plate to the centre of the cell, where it fuses with the plasma membrane. Microfilaments cause constriction (cleavage) of the plasma membrane. Microtubules guide Golgi-derived vesicles to the middle of the cell where they form the cell plate. Neither microtubules nor microfilaments play a role in plant cell cytokinesis.

ANSWER: Vesicles from the Golgi apparatus move along microtubules, coalesce at the plane of cell division, and form a cell plate. The cell plate consists of the plasma membrane and cell wall that will eventually separate the two daughter cells. The plasma membrane of the parent cell grows inward, eventually joining with the cell plate. After chromosome separation is complete, a network of microfilaments forms near the plane of cell division that will separate the two new cells.

Correct In plant cell division, after chromosome separation, the microtubules of the mitotic spindle reorganize into a network that guides vesicles derived from the Golgi apparatus to the plane of cell division. These vesicles begin to fuse, forming the cell plate. As more vesicles are added to the cell plate, it grows outward, eventually fusing with the parent cell plasma membrane. Membrane from the vesicles forms the new plasma membrane for each daughter cell. At the same time, materials that were enclosed in the vesicles form the new cell wall between the new plasma membranes of the daughter cells.

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Part C - The roles of proteins in bacterial cell division and eukaryotic cytokinesis The division of a bacterial cell into two daughter cells (called binary fission) is accomplished by a protein called FtsZ. FtsZ is very similar to the tubulin subunit that form microtubules in eukaryotes. After the replicated bacterial chromosomes have moved to opposite ends of the cell, a ring of FtsZ proteins forms inside the plasma membrane in the region where the cell will divide. As the FtsZ ring constricts, the plasma membrane and bacterial cell wall fold in and eventually separate into two cells.

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.

Hint 1. Comparison of cell walls in plants and bacteria Nearly all plant cells and many bacteria are surrounded by a cell wall. However, the roles these walls play in cell division differ dramatically. In plants, the wall is sufficiently rigid so that in most cells, constriction of a ring of proteins could not cause the wall to fold in and eventually pinch off. Rather, a new plant cell wall is produced between the daughter cells by the formation of a cell plate, which eventually joins with the existing cell wall. In contrast, in bacteria, the cell wall is sufficiently flexible to fold in during constriction of the FtsZ protein ring.

Hint 2. What roles do microfilaments and microtubules or related proteins play in cell division in bacteria, plants, and animals? Bacteria lack the distinct microfilaments and microtubules that dominate the cytoskeletons of plant and animal cells. However, bacteria contain proteins that are similar to actin (the building block of microfilaments) and tubulin (the building block of microtubules). The tubulin-like proteins in bacteria function in the formation of two daughter cells through binary fission. Drag the terms on the left to the appropriate blanks on the right to complete the sentences. ANSWER:

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1. In prokaryotes, constriction of a ring of tubulin-like proteins

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causes infolding of the plasma

membrane and cell wall during cell division (binary fission). 2. In plant cells, a network of microtubules

functions in the formation of the cell plate.

3. In animal cells, a ring of microfilaments constricts, creating a cleavage furrow.

Hint 3. Comparison of cytokinesis in plant and animal cells and bacterial cell division Proteins associated with the cytoskeleton are essential to cytokinesis in plants and animals. Similarly, cytoskeleton-like proteins are essential to cell division in bacteria. The bacterial origin of plants and animals might suggest that these proteins and mechanisms of division are all related; however, evolution is not always that straightforward. Bacterial and animal cells divide in a very similar manner but accomplish division using different proteins. In contrast, plants and bacteria divide in a very different manner but accomplish division using very similar proteins.

ANSWER: Reset

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true false

Correct The physical division of one cell into two during cell division is common to all t...