Biology Ch. 12
A cell biologist carefully measured the quantity of DNA in grasshopper cells growing in cell culture. Cells examined during the G2 phase of the cell cycle contained 200 units of DNA. What would be the amount of DNA at G1 of the cell cycle in one of the grasshopper daughter cells?
100 units *Recall that G2 follows S and that during the S phase, DNA is replicated.
An animal with a diploid number of 36 chromosomes will have ________ chromosomes in its gametes and _________ chromosomes in its somatic cells
18;36
A cell contains 40 chromatids at the beginning of mitosis. How many chromosomes will it contain at the completion of cytokinesis?
20
How many maternal chromosomes are present in a somatic human cell not engaged in cell division?
23
Which of the following structures is/are part of the mitotic spindle?
All of the listed responses are part of the mitotic spindle.
Which of the following statements correctly describes the difference(s) between mitosis and binary fission?
Binary fission involves the replication and division of a single chromosome, whereas mitosis involves the division of multiple, replicated chromosomes
Which of the following is FALSE regarding sister chromatids?
Both of the sister chromatids end up in the same daughter cell after cytokinesis has occurred. * This statement is false. Each of the sisters ends up in a different cell after cell division.
In animal cell mitosis, the cleavage furrow forms during which stage of the cell cycle?
CORRECT ANSWER: Cytokinesis
What is the difference between a benign tumor and a malignant tumor?
Cells of benign tumors do not metastasize; those of malignant tumors do.
What is the difference between a benign tumor and a malignant tumor?
Cells of benign tumors do not metastasize; those of malignant tumors do. * Cells of malignant tumors spread from their site of origin to other parts of the body.
The person credited with first recognizing (in the 1860s) that living cells cannot arise spontaneously, but arise only from previously existing cells, is __________.
Rudolf Virchow *In 1855 Rudolf Virchow stated, "Where a cell exists, there must have been a preexisting cell."
The phase of mitosis during which the chromosomes move toward separate poles of the cell is __________.
anaphase * Anaphase begins when the cohesins joining sister chromatids are cleaved, allowing the chromatids (now called 'chromosomes') to move toward opposite poles of the cell.
The complex of DNA and protein that makes up a eukaryotic chromosome is properly called __________.
chromatin
The complex of DNA and protein that makes up a eukaryotic chromosome is properly called __________.
chromatin * The DNA-protein complex called chromatin is organized into a long, thin fiber.
A cell in G2:
has twice the amount of DNA present in a telophase nucleus.
Chromatids are __________.
identical copies of each other if they are part of the same chromosome
Which of the following processes does NOT occur in dividing bacteria?
mitosis
The _____ is responsible for the separation of the chromosomes during ____ of mitosis.
mitotic spindle, anaphase
DNA replication occurs in __________.
the S phase of interphase
DNA replication occurs in __________.
the S phase of interphase in both somatic and reproductive cells
One event occurring during prophase is __________.
the beginning of the formation of a spindle apparatus
One event occurring during prophase is __________.
the beginning of the formation of a spindle apparatus * During prophase, the mitotic spindle begins to form.
"Cytokinesis" refers to __________.
the division of the cytoplasm *Cytokinesis is the division of the cytoplasm that follows the mitotic division of the nucleus.
During binary fission in a bacterium __________.
the origins of replication move apart
During binary fission in a bacterium, __________.
the origins of replication move apart
Following cytokinesis in an animal cell, how many centrioles does each new daughter cell possess?
two
Assume that you are dealing with a species in which the number of chromosomes in each somatic cell is 14. How many sister chromatids are present in the early telophase of mitosis?
0
If a cell contains 60 chromatids at the start of mitosis, how many chromosomes will be found in each daughter cell at the completion of the cell cycle?
30 * 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.
How many chromatids does a human somatic cell contain after interphase and just prior to mitosis?
92
When a cell in S phase is fused with a cell in G1, __________.
DNA synthesis begins immediately in the original G1 *This observation indicates that cytoplasmic signals can participate in the regulation of the cell cycle.
____ contain identical DNA sequences and are held together by ______ during mitosis
Sister chromatids; centromeres
Which of the following events occurs during metaphase of mitosis?
The chromosomes align along the metaphase plate of the cell.
Which of the following events does not occur during prophase of mitosis?
The mitotic spindle breaks down.
Which of the following events occurs during prometaphase of mitosis? .
The nuclear envelope fragments
How does the process of mitosis differ between most eukaryotes and other eukaryotes such as diatoms and dinoflagellates?
The nuclear envelope fragments in most eukaryotes but remains intact in diatoms and dinoflagellates.
Which of the following events occurs during telophase of mitosis?
Two distinct daughter nuclei form in the cell.
The region of a chromosome holding the two double strands of replicated DNA together is called __________.
a centromere
Observations of cancer cells in culture support the hypothesis that cancer cells _____
a) have altered plasma membranes and cytoskeletal proteins b) have mutations or deletions in tumor suppressors like p53 c) have the ability to stimulate new blood vessel formation d) do not exhibit density-dependent inhibition of growth
A biochemist measured the amount of DNA in cells growing in the laboratory and found that the quantity of DNA in the cells doubled __________.
between the G1 and G2 phases *Between these two phases of the cell cycle, the DNA is replicated during the S phase.
In animal cell mitosis, the cleavage furrow forms during which stage of the cell cycle?
cytokinesis *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.
During interphase, the genetic material of a typical eukaryotic cell is __________.
dispersed in the nucleus as long strands of chromatin
During interphase, the genetic material of a typical eukaryotic cell is __________.
dispersed in the nucleus as long strands of chromatin * During interphase, the chromosomes cannot be distinguished individually because the chromosomes are still in the form of loosely packed chromatin fibers
Which of the following is involved in the binary fission of most bacteria?
distribution of a copy of the single parental chromosome to each daughter cell *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.
Cytokinesis refers to __________.
division of the cytoplasm
Observations of cancer cells in culture support the hypothesis that cancer cells __________.
do not exhibit density-dependent inhibition
You would know a dividing cell was a plant cell rather than an animal cell if you saw that __________.
it had formed a cell plate
Which of the following represents a mismatch or incorrect description?
metaphase: the nuclear envelope disappears * During prometaphase, the nuclear envelope fragments.
In telophase of mitosis, the mitotic spindle breaks down and the chromatin uncoils. This is essentially the opposite of what happens in __________.
prophase * During prophase, we observe the formation of the spindle, the condensation of chromatin, and the disappearance of the nucleolus.
In a human skin cell that is going through the cell cycle, when do the centrosomes separate?
prophase * 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.
Checkpoints in the cell cycle control system __________.
regulate the cell cycle through a variety of stop and go signals
Which of the following does NOT occur during mitosis?
replication of chromosomes
The centromere is a region in which __________.
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.
Which of the following phases of mitosis is essentially the OPPOSITE of prometaphase in terms of the nuclear envelope?
telophase * 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.
A cell is in metaphase if:
the chromosomes are aligned on the equatorial plane of the cell.
If a human somatic cell is just about to divide, it has __________ chromatids.
92 * 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
Down syndrome is characterized by cells having three copies of chromosome 21. As a cell in an individual with Down syndrome prepares to enter mitosis, how many chromatids would be present?
94
Which of the following events does not occur during interphase of the cell cycle?
Separation of the sister chromatids
Which of the following phases of mitosis is essentially the opposite of prometaphase in terms of the nuclear envelope?
Telophase
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?
The DNA was replicated during the S phase of interphase, which occurs between the two G phases
Which of the following hypotheses is best supported by observing cancer cells in a culture?
The cancer cells do not exhibit density-dependent inhibition. * Normal cells respond to density-dependent inhibition by growing in culture to form a single layer of cells.
Which of the following statements describes a cell that undergoes mitosis but not cytokinesis?
The cell contains more than one nucleus.
Which of the following events occurs during anaphase of mitosis?
The sister chromatids are pulled apart toward opposite sides of the cell
The region of a chromosome in which the two double strands of replicated DNA are held together is called __________.
a centromere *The chromosome has a narrow "waist" at a specialized region, called the centromere, where the two chromatids are attached to each other.
During which stage of the cell cycle do sister chromatids separate?
anaphase * Anaphase begins when the cohesins joining sister chromatids are cleaved, allowing the chromatids (now called chromosomes) to move toward opposite poles of the cell.
The function of the mitotic cell cycle is to produce daughter cells that __________.
are genetically identical to the parent cell (assuming no mutation has occurred
The function of the mitotic cell cycle is to produce daughter cells that __________.
are genetically identical to the parent cell (assuming no mutation has occurred) *Cell division involves the distribution of identical genetic material (DNA) to two daughter chromosomes.
One difference between a cancer cell and a normal cell is that
cancer cells continue to divide even when they are tightly packed together.
Tissue culture experiments with PDGF demonstrate that without this substance __________.
fibroblasts fail to divide
Chromatids are __________.
identical copies of each other if they are part of the same duplicated chromosome * Each duplicated chromosome consists of two identical sister chromatids.
You would know that a dividing cell was a plant cell rather than an animal cell if you saw that __________.
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.
At which stage of mitosis are chromosomes lined up in one plane in preparation for their separation to opposite poles of the cell?
metaphase * The chromosomes convene on the metaphase plate, an imaginary plane that is equidistant from the spindle's two poles.
The spread of cancer cells to other locations in the body is known as __________.
metastasis
You would be UNLIKELY to see which of the following human cells dividing?
nerve cell
During what phase in the cell cycle would you find the most DNA per cell?
G2
