Biology 1406 Chapter 12
microtubules attach to kinectocores
prometaphase
Cells will usually divide if they receive the proper signal at a checkpoint in which phase of the cell cycle? -G1 -cytokinesis -M -S -G2
G1
Which of the following correctly matches a phase of the cell cycle with its description? -G2: cell division -M: duplication of DNA -G1: follows cell division -S: immediately precedes cell division -All of the above are correctly matched.
G1: follows cell division
During _____ the cell grows and replicates both its organelles and its chromosomes
Interphase
Nucleoli are present during _____
Interphase
The copying of chromosomes occurs during which of the following phases of the cell cycle? -G1 phase -S phase -G2 phase -M phase
S phase
Which of the following is a function of the S phase in the cell cycle? -The sorting of chromosomes -The synchronization of organelle division -The separation of sister chromatids -The synthesis of sister chromatids
The synthesis of sister chromatids
During interphase, the most of the nucleus is filled with a complex of DNA and protein in a dispersed form called _____
chromatin
The M-phase checkpoint ensures that all chromosomes are attached to the mitotic spindle. If this does not happen, cells would most likely be arrested in ____
metaphase
kinetochores are motionless in relation to poles of cell
metaphase
The _____ is a cell structure consisting of microtubules, which forms during early mitosis and plays a role in cell division
mitotic spindle(s)
The first gap in the cell cycle (G1) corresponds to _____ -the phase between DNA replication and the M phase -the beginning of mitosis -normal growth and cell function -the phase in which DNA is being replicated
normal growth and cell function
At which phase are centrioles beginning to move apart in animal cells? -metaphase -anaphase -prometaphase -prophase
prophase
Starting with a fertilized egg (zygote), a series of five cell divisions would produce an early embryo with how many cells? -16 -64 -32 -8
32
Spindle fibers attach to kinetochores during _____
Prometaphase
During _____ both the contents of the nucleus and the cytoplasm are divided. -S -G1 -mitosis -the mitotic phase -G2
the mitotic phase
If an organism normally has 34 chromosomes, how many molecules of DNA should there be in the G1 phase of the cell cycle? -68 -34 -17 -136
34
A human bone marrow cell, in prophase of mitosis, contains 46 chromosomes. How many chromatids does it contain? -23 or 46, depending on the portion of prophase examined -46 -92 -46 or 92, depending on the portion of prophase examined -23
92
Centromeres divide and sister chromatids become full-fledged chromosomes during _____
Anaphase
The microtubule-organizing center found in animal cells is an identifiable structure present during all phases of the cell cycle. Specifically, it is known as the _____ -microtubulere -centromere -kinetochore -centrosome
Centrosome
In eukaryotic cells, chromosomes are composed of _____ -DNA and proteins -DNA and phospholipids -DNA only -DNA and RNA
DNA and proteins
Which statement provides the best description of the interphase portion of the cell cycle? -Interphase is a brief period between mitosis and chromosome duplication. -During interphase, a cell is metabolically active. -Interphase is a resting stage prior to cell division.
During interphase, a cell is metabolically active
If a eukaryotic cell is in the G1 phase of the cell cycle, which statement about the cell's chromosomes must be correct? -Each chromosome is made of a complex of DNA and associated proteins. -The chromosomes are preparing for DNA synthesis. -Each chromosome consists of two identical chromatids.
Each chromosome is made of a complex of DNA and associated proteins
True or false? The M phase is characterized by the replication and division of a cell's chromosomes
False Correct: Cells replicate their chromosomes during the S phase and divide partition their chromosomes during the M 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 decrease in chromosome number -division of the organism into many cells, most lacking nuclei -large cells containing many nuclei -inability to duplicate DNA -a rapid rate of gamete production
Large cells containing many nuclei
How is plant cell cytokinesis different from animal cell cytokinesis? -The structural proteins of plant cells separate the two cells; in animal cells, a cell membrane separates the two daughter cells. -The contractile filaments found in plant cells are structures composed of carbohydrates; the cleavage furrow in animal cells is composed of contractile phospholipids. -Plant cells divide after metaphase but before anaphase; animal cells divide after anaphase. -Plant cells deposit vesicles containing cell-wall building blocks on the metaphase plate; animal cells form a cleavage furrow.
Plant cells deposit vesicles containing cell-wall building blocks on the metaphase plate; animal cells form a cleavage furrow
Which of the following events would cause the cell cycle to arrest? -Complete chromosome replication -Chromosomes lined up along the metaphase plate -Poor nutrient conditions -Synthesis of cyclins by growth factors and activation of a cyclin-Cdk complex
Poor nutrient conditions
Chromosomes become visible during ____
Prophase
Cytokinesis often, but not always, accompanies ____
Telophase
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? -The cells get smaller with each generation. -The cells do not divide by mitosis. -Frog embryos do not have DNA. -The number of chromosomes decreases with each generation.
The cells get smaller with each generation
Which of the following is true of kinetochores? -They are the primary centromere structures that maintain the attachment of the sister chromatids prior to mitosis. -They are located at the center of the centrosome; their function is to organize tubulin into elongated bundles called spindle fibers. -They interdigitate at the cell's equator and then move apart, causing the cell to elongate. -They are sites at which microtubules attach to chromosomes. -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
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
What is true of all cancers? -They are inherited. -They have escaped normal cell cycle controls. -They are caused by chemical carcinogens.
They have escaped normal cell cycle controls
Why is it difficult to observe individual chromosomes with a light microscope during interphase? -They have uncoiled to form long, thin strands. -The DNA has not been replicated yet. -The spindle must move them to the metaphase plate before they become visible. -Sister chromatids do not pair up until division starts. -They leave the nucleus and are dispersed to other parts of the cell.
They have uncoiled to form long, thin strands
Why do some species employ both mitosis and meiosis, whereas other species use only mitosis? -They need meiosis if the cells are producing organs such as ovaries. -A single-celled organism only needs mitosis. -They need only mitosis to make large numbers of cells such as sperm. -They need both if they are producing animal gametes. -They need only meiosis if they produce egg cells.
They need both if they are producing animal gametes The form of cell division that produces animal gametes is meiosis, not mitosis. The production of gametes in plants is a function of both mitosis and meiosis
Which of the following is true of benign tumors, but not malignant tumors? -They remain confined to their original site -They migrate from the initial site of transformation to other organs or tissues. -They are the result of the transformation of normal cells. -They can divide indefinitely if an adequate supply of nutrients is available. -They have an unusual number of chromosomes.
They remain confined to their original site
A cleavage furrow is ____ -a ring of vesicles forming a cell plate -a groove in the plasma membrane between daughter nuclei -the space that is created between two chromatids during anaphase -the separation of divided prokaryotes
a groove in the plasma membrane between daughter nuclei
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 _____ -a plant cell in metaphase -an animal cell in the S phase of the cell cycle -an animal cell in the process of cytokinesis -a plant cell in the process of cytokinesis
a plant cell in the process of cytokinesis
Cohesins breaks down Kinectocores move toward poles of cell
anaphase
Metaphase is characterized by _____ -separation of sister chromatids -aligning of chromosomes on the equator -cytokinesis -splitting of the centromeres
aligning of chromosomes on the equator
After chromosomes condense, the ____ is the region where the identical DNA molecules are most tightly attached to each other
centromere(s)
The ________ are the organizing material for microtubules involved in separating chromosomes during mitosis
centrosome(s)
One difference between cancer cells and normal cells is that cancer cells -are always in the M phase of the cell cycle. -cannot function properly because they are affected by density-dependent inhibition. -are arrested at the S phase of the cell cycle. -are unable to synthesize DNA. -continue to divide even when they are tightly packed together
continue to divide even when they are tightly packed together
In most eukaryotes, the division of the nucleus is followed by ____, when the rest of the cell divides
cytokensis
During telophase, the nonkinectocore microtubules _____
disassemble
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 -suppression of cyclin production. -inhibition of regulatory protein phosphorylation. -disruption of mitotic spindle formation -myosin denaturation and inhibition of cleavage furrow formation. -inhibition of DNA synthesis.
disruption of mitotic spindle formation
What is the final result of mitosis in a human? -genetically different 2n somatic cells -genetically identical 2n somatic cells -genetically identical 1n somatic cells -genetically identical 2n gamete cells
genetically identical 2n somatic cells
Neurons and some other specialized cells divide infrequently because they ____ -can no longer bind Cdk to cyclin -show a drop in MPF concentration -no longer have active nuclei -have entered into G0
have entered into G0
Scientists isolate cells in various phases of the cell cycle. They find a group of cells that have 1.5 times more DNA than G1 phase cells. The cells of this group are _____. -in the S phase of the cell cycle -in the M phase of the cell cycle -between the G1 and S phases in the cell cycle -in the G2 phase of the cell cycle
in the S phase of the cell cycle
In dividing cells, the cells most growth is during ____
interphase
During mitosis, micro-tubules attach to the chromosomes at _____
kinetchore(s)
Besides the ability of some cancer cells to overproliferate, what else could logically result in a tumor? -inability of chromosomes to meet at the metaphase plate -lack of appropriate cell death -inability to form spindles -changes in the order of cell cycle stages
lack of appropriate cell death
During prohase, the microtubulues of mitotic spindle _____
lengthen
During anaphase, the nonkinectochore microtubules ______ and move past each other, and kinectocore microtubules ______
lengthen shorten
Tubulins assemble into spindle microtubules Cohesins join sister chromatids of duplicated chromosomes
prophase
The mitotic spindle is a microtubular structure that is involved in ___ -dissolving the nuclear membrane -triggering the compaction and condensation of chromosomes -splitting of the cell (cytokinesis) following mitosis -separation of sister chromatids
separation of sister chromatids
DNA replication produces two identical DNA molecules, called ____, which separate during mitosis
sister chromatids
spindle microtublules dissassemble
telophase
In human and many other eukaryotic species' cells, the nuclear membrane has to disappear to permit _____ -the disassembly of the nucleolus -the attachment of microtubules to kinetochores -cytokinesis -the splitting of the centrosomes
the attachment of microtubules to kinetochores
Taxol is an anticancer drug extracted from the Pacific yew tree. In animal cells, Taxol disrupts microtubule formation. Surprisingly, this stops mitosis. Specifically, Taxol must affect _____ -the structure of the mitotic spindle -chromatid assembly -formation of the centrioles -anaphase
the structure of the mitotic spindle
During prophase a homologous pair of chromosomes consists of ____ -two chromosomes and four chromatids -two chromosomes and two chromatids -one chromosome and four chromatids -four chromosomes and two chromatids -one chromosome and two chromatids
two chromosomes and four chromatids At this point each of the chromosomes consists of two chromatids
Consider an animal cell in which motor proteins in the kinetochores normally pull the chromosomes along the kinetochore microtubules during mitosis. Suppose, however, that during metaphase, this cell was treated with an inhibitor that blocks the function of the motor proteins in the kinetochore, but allows the kinetochore to remain attached to the spindle. The inhibitor has no effect on any other mitotic process, including the function of the nonkinetochore microtubules. Will the cell elongate during mitosis? Will the sister chomatids separate from each other? Will the chromosomes move to the poles of the cell?
yes yes no
