a. Anton van Leeuwenhoek
b. Rudolf Virchow
c. Robert Hooke
d. Louis Pasteur
In 1855 Rudolf Virchow stated, “Where a cell exists, there must have been a preexisting cell.”
a. have a random assortment of maternal and paternal chromosomes
b. have the same number of chromosomes as the parent cell but not the same genetic content
c. have the same number of chromatids as the parent cell had chromosomes
d. are genetically identical to the parent cell (assuming no mutation has occurred)
e. have none of the listed characteristics
Cell division involves the distribution of identical genetic material (DNA) to two daughter chromosomes.
a. Both of the sister chromatids end up in the same daughter cell after cytokinesis has occurred.
b. Sister chromatids are created when DNA is replicated.
c. Sister chromatids are separated during mitosis.
d. Sister chromatids are attached to one another at the centromere.
e. Sister chromatids form in the S-phase stage of the cell cycle.
This statement is false. Each of the sisters ends up in a different cell after cell division.
a. a centromere
b. a chromoplast
c. a chromatid
e. a centrosome
The DNA-protein complex called chromatin is organized into a long, thin fiber.
a. a centriole
b. an aster
d. a chromatid
e. a centromere
The chromosome has a narrow “waist” at a specialized region, called the centromere, where the two chromatids are attached to each other.
a. chromosomes become aligned during metaphase
b. microtubules are fastened to the centrioles during anaphase
c. the new cell plate forms in telophase
d. the chromosomes are connected to the cell plate in metaphase
e. sister chromatids are attached to one another in prophase
The chromosome has a narrow “waist” at a specialized region called the centromere, where sister chromatids are attached.
e. None of the listed responses is correct.
Human somatic cells contain a total of 46 chromosomes, half of which are maternally derived.
a. 16 chromosomes
b. 64 chromosomes
c. 32 pairs of chromosomes
d. 64 pairs of chromosomes
e. none of the listed numbers of chromosomes
There would be 32 chromosomes present in each of the daughter cells.
a. the reduction in the number of chromosomes
b. the division of the entire cell
c. the division of the cytoplasm
d. the division of the nucleus
e. the movement of a cell from one place to another
Cytokinesis is the division of the cytoplasm that follows the mitotic division of the nucleus.
a. held together by the centrioles
b. the bacterial equivalent of eukaryotic chromosomes
c. found only in aberrant chromosomes
d. composed of RNA
e. identical copies of each other if they are part of the same duplicated chromosome
Each duplicated chromosome consists of two identical sister chromatids.
In this case, mitosis starts with 30 chromosomes, each of which consists of two chromatids. At the completion of mitosis, each daughter cell will contain 30 chromosomes.
a. between prophase and anaphase
b. between the G2 phase and prophase
c. between anaphase and telophase
d. during the M phase of the cell cycle
e. between the G1 and G2 phases
Between these two phases of the cell cycle, the DNA is replicated during the S phase.
a. 50 units
b. 100 units
c. between 50 and 100 units
d. 200 units
e. 400 units
Recall that G2 follows S and that during the S phase, DNA is replicated.
a. dispersed in the cytoplasm as long strands of chromatin
b. condensed and the chromosomes are often visible under the light microscope
c. dispersed in the nucleus as long strands of chromatin
d. attached to microtubule spindle fibers
e. transported through the nuclear pores
During interphase, the chromosomes cannot be distinguished individually because the chromosomes are still in the form of loosely packed chromatin fibers.
b. the G1 phase of interphase
c. the S phase of interphase
d. metaphase of mitosis
e. prophase of mitosis
Chromosomes are duplicated only during the S phase (“S” stands for synthesis of DNA).
e. There is insufficient information to answer the question.
Human somatic cells have 92 chromatids just prior to cell division due to the replication of the 46 chromosomes that occurred during the S phase.
Cells from an individual with Down syndrome would have 23 pairs of chromosomes, plus an extra chromosome for a total of 47. At S phase those chromosomes replicate to produce 94 sister chromatids.
a. separation of chromatids
b. condensation of chromatin
c. alignment of chromosomes along the cell’s equator
d. the movement of chromosomes to opposite poles
e. replication of chromosomes
The DNA of the chromosomes is replicated in the S phase before mitosis.
Chromosomes are duplicated only during the S phase (“S” stands for synthesis of DNA). The phase following completion of the S phase is G2.
b. S phase
During prophase, we observe the formation of the spindle, the condensation of chromatin, and the disappearance of the nucleolus.
b. S phase
In prometaphase the nuclear envelope fragments and the kinetochores attach to microtubules. During telophase, fragments of the nuclear envelope begin to reassemble along with portions of the endomembrane system.
e. None of the listed responses is correct.
By telophase, the chromatids have separated and the individual units of DNA (now called chromosomes) are arriving at the poles. There are no chromatids at this point.
a. S phase
d. G2 phase
The centrosomes move away from each other during prophase, apparently propelled along the surface of the nucleus by the lengthening bundles of microtubules between them.
Each daughter cell inherits a single centrosome following cytokinesis and each centrosome contains two centrioles.
Anaphase begins when the cohesins joining sister chromatids are cleaved, allowing the chromatids (now called ‘chromosomes’) to move toward opposite poles of the cell.
a. the alignment of chromosomes in a single plane
b. the synthesis of a new nuclear envelope
c. the beginning of the formation of a spindle apparatus
d. the division of the centromere
During prophase, the mitotic spindle begins to form.
a. Genetically identical chromosomes (previously sister chromatids) move to opposite poles during anaphase.
b. A spindle made of microtubules is present during anaphase.
c. Cohesins joining sister chromatids at the centromeres are cleaved during anaphase.
d. The centrioles are at opposite poles during anaphase.
e. All of the listed responses are correct.
Anaphase begins when the cohesins connecting sister chromatids are cleaved, liberating the chromatids (now called chromosomes), which begin moving toward opposite poles of the cell.
a. telophase: chromosomes become more extended
b. anaphase: there is movement of the chromosomes to the poles
c. metaphase: the nuclear envelope disappears
d. metaphase: chromosomes line up on the equatorial plane
e. prophase: chromosomes become more tightly coiled
During prometaphase, the nuclear envelope fragments.
c. G1 phase
e. G2 phase
Anaphase begins when the cohesins joining sister chromatids are cleaved, allowing the chromatids (now called chromosomes) to move toward opposite poles of the cell.
b. the G1 phase
Cytokinesis is usually well under way by telophase. In animal cells, cytokinesis involves the formation of a cleavage furrow, which pinches the cell in two.
The chromosomes convene on the metaphase plate, an imaginary plane that is equidistant from the spindle’s two poles.
a. it had formed a cleavage furrow
b. it had microtubules
c. it had two pairs of centrioles during prophase
d. the nucleolus was visible during metaphase
e. it had formed a cell plate
The cell plate, which divides the cytoplasm in two, forms during the telophase of mitosis in a plant cell.
a. binary fission
c. inward growth of the plasma membrane
d. replication of DNA
e. separation of the origins of replication
Mitosis does not occur in dividing bacteria. Mitosis might have had its origins in simpler bacterial mechanisms of cell reproduction. Prokaryotes (bacteria) reproduce by a type of cell division called binary fission.
a. the two DNA molecules attach to the centrioles
b. the two DNA molecules divide in half, forming four DNA fragments
c. the two DNA molecules break up into plasmids
d. the origins of replication move apart
e. the two DNA molecules float free in the cell and are guided to daughter cells by a spindle-like apparatus
This occurs during binary fission.
a. distribution of a copy of the single parental chromosome to each daughter cell
b. formation of a cell plate
c. disintegration of the nuclear membrane
d. formation of a spindle apparatus
e. prophase, prometaphase, metaphase, anaphase, and telophase
Prokaryotes reproduce by a type of cell division called binary fission, which involves replicating the single chromosome and distributing the copies equally to two daughter cells.
a. the original G1 cell will divide immediately
b. the two nuclei fuse and additional division is arrested
c. the replication of DNA occurring in the original S nucleus is terminated
d. DNA synthesis begins immediately in the original G1 nucleus
e. the chromosomes of the original G1 nucleus condense in preparation for mitosis
This observation indicates that cytoplasmic signals can participate in the regulation of the cell cycle.
a. bacterial cells lose their resistance to antibiotics
b. fibroblasts fail to divide
c. the various kinases, such as MPF, are unable to bind to cyclin
d. animal cells are unable to attach to the substratum
e. cells divide in an uncontrolled fashion, confirming PDGF’s role as a cell division inhibitor
PDGF is a specific growth factor for fibroblasts.
a. skin cell
b. cell from an embryo
c. cancer cell
d. nerve cell
e. All of these cell types are equally unlikely to divide at any given time.
Nerve cells are quite complex and specialized. After reaching maturity, they enter the G0 phase.
a. The cancer cells exhibit anchorage dependence.
b. The cancer cells spend the majority of their time in the G0 phase.
c. The cancer cells do not exhibit density-dependent inhibition.
d. The cancer cells produce molecules that inhibit the growth factors required for cell division.
e. All of the listed responses are correct.
Normal cells respond to density-dependent inhibition by growing in culture to form a single layer of cells.
a. Benign tumors will not kill you; malignant tumors will.
b. Benign tumors arise by transformation; malignant tumors do not.
c. Benign tumors do not arise by transformation; malignant tumors do.
d. Cells of benign tumors do not metastasize; those of malignant tumors do.
e. Cells of benign tumors metastasize; those of malignant tumors do not.
Cells of malignant tumors spread from their site of origin to other parts of the body.
a. a bacterial cell dividing.
b. an animal cell in the process of cytokinesis.
c. a plant cell in the process of cytokinesis.
d. a plant cell in metaphase.
e. an animal cell in the S phase of the cell cycle.
a. inhibition of regulatory protein phosphorylation.
b. myosin denaturation and inhibition of cleavage furrow formation.
c. disruption of mitotic spindle formation.
d. suppression of cyclin production.
e. inhibition of DNA synthesis.
a. are always in the M phase of the cell cycle.
b. are unable to synthesize DNA.
c. continue to divide even when they are tightly packed together.
d. cannot function properly because they are affected by density-dependent inhibition.
e. are arrested at the S phase of the cell cycle.
a. synthesis of DNA.
b. the degradation of cyclin.
c. the destruction of the protein kinase Cdk.
d. the accumulation of cyclin.
e. decreased synthesis of Cdk.
a. cells lacking nuclei.
b. destruction of chromosomes.
c. cells that are unusually small.
d. cell cycles lacking an S phase.
e. cells with more than one nucleus.
a. separation of the spindle poles
b. separation of sister chromatids
c. replication of the DNA
d. spindle formation
e. condensation of the chromosomes
a. spindle attachment to kinetochores
b. cell elongation during anaphase
c. DNA synthesis
d. spindle formation
e. cleavage furrow formation and cytokinesis
a. a chromosome in G1 of the cell cycle
b. a replicated chromosome
c. a chromosome found outside the nucleus
d. a special region that holds two centromeres together
e. another name for the chromosomes found in genetics
a. The daughter cells have half the amount of cytoplasm and half the amount of DNA.
b. The daughter cells have half the number of chromosomes and half the amount of DNA.
c. The daughter cells have the same number of chromosomes and half the amount of DNA.
d. The daughter cells have the same number of chromosomes and the same amount of DNA.
e. The daughter cells have the same number of chromosomes and twice the amount of DNA.
a. an animal cell in metaphase
b. an animal cell in telophase
c. an animal cell undergoing cytokinesis
d. a plant cell in metaphase
e. a plant cell undergoing cytokinesis
a. Chromatids must lose their kinetochores.
b. Cohesin must attach the sister chromatids to each other.
c. Cohesin must be cleaved enzymatically.
d. Kinetochores must attach to the metaphase plate.
e. Spindle microtubules must begin to depolymerize.
a. to increase their potential energy
b. to allow the chromosomes to move without becoming entangled and breaking
c. to allow the chromosomes to fit within the nuclear envelope
d. to allow the sister chromatids to remain attached
e. to provide for the structure of the centromere
a. Normal cells complete a limited number of divisions before they age and die.
b. Cancer cells can be metastatic if they have abnormal changes on their cell surfaces.
c. Normal human cells have a characteristic number of chromosomes.
d. Cancer cells have the ability to stimulate blood vessels to grow towards the tumor.
e. Normal cells are better able to repair DNA damaged by high energy radiation.
f. All of the above are correct.
g. All of the above are false.
a. reduces cyclin concentrations.
b. increases cyclin concentrations.
c. prevents elongation of microtubules.
d. prevents shortening of microtubules.
e. prevents attachment of the microtubules to the kinetochore.
a. a single large nucleus.
b. high concentrations of actin and myosin.
c. two abnormally small nuclei.
d. two nuclei.
e. two nuclei but with half the amount of DNA.