Chapter 12: The Cell Cycle

In animal cell mitosis, the cleavage furrow forms during which stage of the cell cycle? a. Cytokinesis b. Anaphase c. The G1 phase d. Metaphase e. Prophase

a. Cytokinesis Explanation: In animal cells, cytokinesis occurs by a process known as cleavage. The first sign of cleavage is the appearance of a cleavage furrow, a shallow groove in the cell surface near the old metaphase plate.

Which of the following statements describes a cell that undergoes mitosis but not cytokinesis? a. The cell contains more than one nucleus. b. The cell does not contain a nucleus. c. The cell has one nucleus. d. The cell has undergone transformation and become a cancer cell. e. The cell dies. f. The cell has not proceeded through interphase.

a. The cell contains more than one nucleus Explanation: The cell would have one nucleus if cytokinesis occurred. Any cell that has undergone mitosis still has at least one nucleus. There is not enough information to determine if transformation of the cell occurred. Since the cell went through mitosis, it had to go through interphase. It cannot be determined if the cell died.

Which of the following statements correctly describes the difference(s) between mitosis and binary fission? a. binary fission involves the replication and division of a single chromosome, whereas mitosis involves the division of multiple, replicated chromosomes b. there are no differences between binary fission and mitosis c. binary fission in bacteria is completed by microtubules, but mitosis does not involve these structures. d. binary fission involves the replication and division of multiple chromosomes, whereas mitosis involves the replication and division of a single chromosome e. a cell plate forms across the middle of two cells dividing by binary fission, but does not occur in mitosis

a. binary fission involves the replication and division of a single chromosome, whereas mitosis involves the division of multiple, replicated chromosomes Explanation: There are many differences between binary fission and mitosis. Binary fission involves the division of a single chromosome, and mitosis involves the division of multiple chromosomes. A cell plate forms across the middle of a plant cell, not a bacterial cell. Binary fission does not involve microtubules, but mitosis does.

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. cells of benign tumors metastasize; those of malignant tumors do not. c. benign tumors do not arise by transformation; malignant tumors do. 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.

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

a. division of the cytoplasm Explanation: Mitosis, the division of the genetic material in the nucleus, is usually followed immediately by cytokinesis, the division of the cytoplasm. One cell has become two, each the genetic equivalent of the parent cell. Cytokinesis does not involve the division of chromosomes, nor does it involve any cellular movement.

The spread of cancer cells to other locations in the body is known as __________. a. metastasis b. a benign tumor c. density-dependent inhibition d. transformation e. chemotherapy

a. metastasis Explanation: Chemotherapy is a type of cancer treatment. Density-dependent inhibition is the effect of an external physical factor on cell division. Transformation is the process that causes normal cells to act like cancer cells. A benign tumor is one that does not spread to other parts of the body.

Checkpoint in the cell cycle control system _______________. a. regulate the cell cycle through a variety of stop and go signals b. ensure that a cell keeps dividing c. only stop cells from dividing d. only signal cells to undergo mitosis e. have no effect on the cell cycle f. stop cancer cells from dividing

a. regulate the cell cycle through a variety of stop and go signals Explanation: The cell cycle control system regulates whether cell division proceeds. The cell cycle control system can initiate or stop cell division. The cell cycle control system regulates cell division. The cell cycle control system does not function properly in cancer cells.

DNA replication occurs in ___________. a. the S phase of interphase in both somatic and reproductive cells b. metaphase of meiosis only c. the cytokinesis portion of the cell's life cycle d. prophase of both mitosis and meiosis e. the G1 phase of interphase in reproductive cells only

a. the S phase of interphase in both somatic and reproductive cells Explanation: Chromosomes are duplicated only during the S phase ("S" stands for synthesis of DNA) of interphase of the cell cycle. During all three subphases, a cell that will eventually divide grows by producing proteins and cytoplasmic organelles such as mitochondria and endoplasmic reticulum.

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

a. the beginning of the formation of a spindle apparatus Explanation: During prophase, chromatin condenses into distinct chromosomes, the nucleolus disappears, and the mitotic spindle apparatus begins to form. During metaphase, the mitotic spindle aligns the chromosomes at the metaphase plate, a region along the equator of the cell. Anaphase begins when the paired centromeres of each chromosome separate, liberating the sister chromatids, which begin moving toward opposite poles of the cell. In telophase, a new nuclear envelope begins to synthesize, the mitotic spindle breaks down, the chromatin uncoils, and cytokinesis begins.

Which of the following events does not occur during prophase of mitosis? a. the mitotic spindle breaks down b. the chromosomes condense c. each duplicated chromosome appears as two identical sister chromatids d. the mitotic spindle forms e. nucleoli disappear f. the centrosomes move away from each other

a. the mitotic spindle breaks down

Which of the following events does not occur during prophase of mitosis? a. the mitotic spindle breaks down b. the mitotic spindle forms c. nucleoli disappear - d. the centrosomes move away from each other e. each duplicated chromosome appears as two identical sister chromatids - f. the chromosomes condense

a. the mitotic spindle breaks down Explanation: *it occurs during telophase, not prophase The mitotic spindle forms during prophase of mitosis. The chromosomes condense during prophase of mitosis. The nucleoli disappear during prophase of mitosis. The centrosomes move away from each other during prophase of mitosis. Each duplicated chromosome appears as two identical sister chromatids during prophase of mitosis.

Which of the following events does not occur during prophase of mitosis? a. the mitotic spindle breaks down b. the chromosomes condense c. each duplicated chromosome appears as two identical sister chromatids d. the mitotic spindle forms e. nucleoli disappear f. the centrosomes move away from each other

a. the mitotic spindle breaks down Explanation: The mitotic spindle forms during prophase of mitosis. The chromosomes condense during prophase of mitosis. The nucleoli disappear during prophase of mitosis. The centrosomes move away from each other during prophase of mitosis. Each duplicated chromosome appears as two identical sister chromatids during prophase of mitosis.

The complex of DNA and protein that makes up a eukaryotic chromosome is properly called ____________. a. a chromoplast b. chromatin c. a chromatid - d. a centromere e. a centrosome

b. chromatin Explanation: the entire complex of DNA and proteins that is the building material of chromosomes is referred to as chromatin. A centromere is the narrow region of the chromosome where the two duplicated chromosomes, sister chromatids, attach to one another. A chromoplast is a pigment-storing organelle and the centrosome is the organelle from which microtubules originate.

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

b. dispersed in the nucleus as long strands of chromatin

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

b. dispersed in the nucleus as long strands of chromatin Explanation: During interphase, the chromosomes cannot be distinguished individually under a light microscope because they are still in the form of loosely packed chromatin fibers. In addition, the nucleus is still intact during interphase, with the genetic material inside. The chromosomes do not condense until prophase of mitosis, when the spindle fibers attach to them. Unlike RNA and proteins, the DNA does not typically leave the nucleus.

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

b. identical copies of each other if they are part of the same chromosome Explanation: Each sister chromatid has a centromere, a region containing specific DNA sequences where the chromatid is attached most closely to its sister chromatid. Centrioles do not hold chromatids together. Centrioles are involved in distributing chromosomes to daughter cells during mitosis. Bacterial cells have a single, circular chromosome, whereas chromatids are found only in eukaryotic cells.

Which of the following events does not occur during interphase of the cell cycle? a. production of new mitochondria b. separation of the sister chromatids c. duplication of the chromosomes d. growth of the cell e. protein production f. production of the endoplasmic reticulum

b. separation of the sister chromatids Explanation: *Separation of the sister chromatids does not occur during interphase. Instead, this process occurs during anaphase of mitosis. Duplication of the chromosomes occurs during the S phase of interphase. Growth of the cell occurs during the G1 and G2 phases of interphase. Production of new mitochondria occurs during all three phases of interphase. Protein production occurs during all three phases of interphase. Endoplasmic reticulum production occurs during all three phases of interphase.

Which of the following phases of mitosis is essentially the opposite of prometaphase in terms of the nuclear envelope? a. S phase b. Telophase c. Metaphase d. Interphase e. Anaphase

b. telophase Explanation: In prometaphase, which is essentially the opposite of telophase, the nuclear envelope fragments and the kinetochores attach to microtubules. During metaphase, the mitotic spindle aligns the chromosomes at the metaphase plate, a region along the equator of the cell. In telophase, fragments of the nuclear envelope begin to reassemble, the mitotic spindle breaks down, the chromatin uncoils, and cytokinesis begins. The S phase is part of interphase and not part of mitosis.

A cell biologist examined the DNA content of a cell from a fruit fly larva during the G1 phase and determined that it had 150 units of DNA. After measuring the DNA content of the same type of cell after the G2 phase, it was discovered that the cell had 300 units of DNA. How is this possible? a. The DNA was not replicated. This was the result of a mutation. b. The DNA was replicated after the G2 phase of interphase. c. The DNA was replicated during the S phase of interphase, which occurs between the two G phases. d. The DNA was replicated during the G2 phase of interphase. e. The DNA was replicated prior to interphase. f. The DNA was replicated during the G1 phase of interphase.

c. The DNA was replicated during the S phase of interphase, which occurs between the two G phases.

The function of the mitotic cell cycle is to produce daughter cells that ________________. a. have the same number of chromosomes as the parent cell but not the same genetic content b. have a random assortment of maternal and paternal chromosomes c. are genetically identical to the parent cell (assuming no mutation has occurred) d. have the same number of chromatids as the parent cell had chromosomes e. none of the listed are correct

c. are genetically identical to the parent cell (assuming no mutation has occurred)

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

c. the origins of replication move apart Explanation: Bacteria lack a spindle apparatus and centrioles. In addition, at the origin of replication, the circular DNA molecule is replicated, forming two, not four, identical copies of the bacterial chromosome.

A cell contains 40 chromatids at the beginning of mitosis. How many chromosomes will it contain at the completion of cytokinesis? a. 10 b. 40 c. 80 d. 20 e. 160 f. 5

d. 20 Explanation: Each duplicated chromosome has two sister chromatids, which are joined copies of the original chromosome. the two sister chromatids of each duplicated chromosome separate and move into two new nuclei, one forming at each end of the cell. The number of chromosomes in a cell at the end of mitosis is half as many as the number of sister chromatids the cell had at the beginning of mitosis.

The region of a chromosome holding the two double strands of replicated DNA together is called ______________. a. an aster b. a chromatid c. chromatin d. a centromere e. a centriole

d. a centromere

Observation of cancer cells in culture support the hypothesis that cancer cells _____. a. spend the majority of their time in the G0 phase b. produce molecules that inhibit the growth factors required for cell division - c. exhibit anchorage dependence d. do not exhibit density-dependent inhibition

d. do not exhibit density-dependent inhibition Explanation: density-dependent inhibition, a phenomenon in which crowded cells stop dividing Cancer cells do not heed the normal signals that regulate the cell cycle. They divide excessively and invade other tissues. cancer cells divide uncontrollably, they do not produce molecules that inhibit the growth factors required for cell division Cancer cells are characterized by the lack of anchorage dependence. Cells in the G0 phase have assumed a nondividing state, which does not describe cancer cells.

How does the process of mitosis differ between most eukaryotes and other eukaryotes such as diatoms and dinoflagellates? a. the chromosomes are not duplicated prior to mitosis in diatoms and dinoflagellates b. the nuclear envelope remains intact in most eukaryotes but fragments in diatoms and dinoflagellates c. sister chromatids are not separated during mitosis in diatoms and dinoflagellates d. the nuclear envelope fragments in most eukaryotes but remains intact in diatoms and dinoflagellates e. microtubules do not facilitate the movement of chromosomes in diatoms and dinoflagellates

d. the nuclear envelope fragments in most eukaryotes but remains intact in diatoms and dinoflagellates Explanation: In most eukaryotes, the nuclear envelope fragments during mitosis. This does not occur in diatoms and dinoflagellates. Microtubules facilitate the movement of chromosomes in mitosis in all eukaryotes. Chromosomes are duplicated prior to mitosis in all eukaryotes. Sister chromatids separate during mitosis in diatoms and dinoflagellates.

How many chromatids does a human somatic cell contain after interphase and just prior to mitosis? a. 23 b. 69 c. 184 d. 22 e. 92 f. 46

e. 92 Explanation: Each duplicated chromosome has two sister chromatids, which are joined copies of the original chromosome.

Which event or events occur during anaphase? a. the centromeres divide b. a spindle made of microtubules is present c. identical chromatids move to opposite poles d. the centrioles are at opposite poles e. All of the listed responses are correct

e. All of the listed responses are correct

Which of the following structures is/are part of the mitotic spindle? a. nonkinetochore microtubules b. centrosome c. the aster d. kinetochore microtubules e. All of the listed responses are part of the mitotic spindle.

e. All of the listed responses are part of the mitotic spindle.

Which of the following events occur during the metaphase of mitosis? a. the nuclear envelope forms again b. the nuclear envelope disappears c. the mitotic spindle forms d. the chromosomes condense e. the sister chromatids are pulled apart toward opposite sides of the cell f. the chromosomes align along the metaphase plate of the cell

f. the chromosomes align along the metaphase plated of the cell Explanation: The nuclear envelope disappears during prometaphase of mitosis. The chromosomes condense during prophase of mitosis. The sister chromatids are pulled apart toward opposite sides of the cell during anaphase of mitosis. The nuclear envelope forms again during telophase of mitosis. The mitotic spindle forms during prophase of mitosis.

Which of the following events occurs during prometaphase of mitosis? a. the nuclear envelope forms again b. the centrosomes move away from each other c. the mitotic spindle forms d. the chromosomes align along the metaphase plate of the cell. e. the sister chromatids are pulled toward opposite sides of the cell. f. the nuclear envelope fragments

f. the nuclear envelope fragments Explanation: The centrosomes move away from each other during prophase of mitosis. The chromosomes align along the metaphase plate of the cell during metaphase of mitosis. The mitotic spindle forms during prophase of mitosis. The nuclear envelope forms again during telophase of mitosis. The sister chromatids are pulled toward opposite sides of the cell during anaphase of mitosis.

Which of the following events occurs during anaphase of mitosis? a. spindle fibers attach to the centromeres of the chromosomes b. the nuclear envelope fragments c. the mitotic spindle forms d. the nuclear envelope forms again e. the chromosomes align along the metaphase plate of the cell f. the sister chromatids are pulled apart toward opposite sides of the cell

f. the sister chromatids are pulled apart toward opposite sides of the cell

What event occurs during telophase of mitosis? a. the chromosomes align on the metaphase plate b. the chromosomes condense c. DNA replicates d. the nuclear envelope fragments e. the sister chromatids separate f. two distinct daughter nuclei form in a cell

f. two distinct daughter nuclei form in a cell Explanation: The nuclear envelope fragments during prometaphase of mitosis. The chromosomes align on the metaphase plate during metaphase of mitosis. The sister chromatids separate during anaphase of mitosis. The chromosomes condense during prophase of mitosis. DNA replicates during interphase.