Chapter 12 Questions Flashcards
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 the process of cytokinesis
Vinblastine is a standard chemotherapeutic drug used to treat cancer. Because it interferes with the assembly of microtubules, its effectiveness must be related to
disruption of mitotic spindle formation
One difference between cancer cells and normal cells is that cancer cells
continue to divide even when they are tightly packed together
The decline of MPF activity at the end of mitosis is due to
the degradation of cyclin
In the cells of some organisms, mitosis occurs without cytokinesis. This will result in
cells with more than one nucleus
Which of the following does NOT occur during mitosis?
replication of DNA
Which of the following DOES occur in mitosis?
- condensation of the chromosomes
- separation of sister chromatids
- spindle formation
- separation of the spindle pores
A particular cell has half as much DNA as some other cells in a mitotically active tissue. The cell in question is most likely in
G1
The drug cytochalasin B blocks the function of actin. Which of the following aspects of the animal cell cycle would be most disrupted by cytochalasin B?
cleavage furrow formation and cytokinesis
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.
Which of the following is true regarding sister chromatids?
- sister chromatids are separated during mitosis
- sister chromatids form in the S-phase stage of the cell cycle
- sister chromatids are attached to one another at the centromere
- sister chromatids are created when DNA is replicated
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.
The region of a chromosome holding the two double strands of replicated DNA 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.
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.
How many maternal chromosomes are present in a somatic human cell not engaged in cell division?
23
-Human somatic cells contain a total of 46 chromosomes, half of which are maternally derived.
A cell entering the cell cycle with 32 chromosomes will produce two daughter cells, each with _____.
There would be 32 chromosomes present in each of the daughter cells.
“Cytokinesis” refers to _____.
division of the cytoplasm
-Cytokinesis is the division of the cytoplasm that follows the mitotic division of the nucleus.
Chromatids are _____.
identical copies of each other if they are part of the same chromosome
-Each duplicated chromosome consists of two identical sister chromatids.
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.
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.
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.
During interphase, the genetic material of a typical eukaryotic cell is _____.
dispersed in the nucleus as long strands of chromatin
DNA replication occurs in _____.
the S phase of interphase in both somatic and reproductive cells
-Chromosomes are duplicated only during the S phase (“S” stands for synthesis of DNA).
If a somatic human cell is just about to divide, it has _____ chromatids.
92
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
-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.
Which of the following does NOT occur during mitosis?
replication of chromosomes
-The DNA of the chromosomes is replicated in the S phase before mitosis.
During what phase in the cell cycle would you find the most DNA per cell?
G2
-Chromosomes are duplicated only during the S phase (“S” stands for synthesis of DNA). The phase following completion of the S phase is G2.
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.
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.
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
In a human skin cell that is going through the cell cycle, when do the centrosomes separate?
prophase
Following cytokinesis in an animal cell, how many centrioles does each new daughter cell possess?
two
-Each daughter cell inherits a single centrosome following cytokinesis and each centrosome contains two centrioles.
The phase of mitosis during which the chromosomes move toward separate poles of the cell is _____.
anaphase