Mastering Biology Ch. 12 (Mitosis)
During interphase, most of the nucleus is filled with a complex of DNA and protein in a dispersed form called __________.
chromatin
Cytochalasin B is a chemical that disrupts microfilament formation. How would this interfere with cell division?
cleavage
In what way do kinetochore microtubules facilitate the process of splitting the centromeres?
they create tension by pulling toward opposite poles
Why is it difficult to observe individual chromosomes with a light microscope during interphase?
they have uncoiled to form long, thin strands
In a diploid cell with 5 chromosome pairs (2n = 10), how many centromeres will be found in a nucleus at G2 of the cell division cycle?
10
A group of cells is assayed for DNA content immediately following mitosis and is found to have an average of 8 picograms of DNA per nucleus. How many picograms of DNA would be found in a nucleus at prophase of mitosis?
16
If there are 40 centromeres in a cell at anaphase of mitosis, how many chromosomes will be found in each daughter cell following cytokinesis?
20
In a diploid cell with 5 chromosome pairs (2n = 10), how many sister chromatids will be found in a nucleus at prophase of mitosis?
20
Starting with a fertilized egg (zygote), a series of six cell divisions would produce an early embryo with how many cells?
64
A human bone marrow cell, in prophase of mitosis, contains 46 chromosomes. How many chromatids does it contain?
92
What is true of all cancers?
They have escaped normal cell cycle controls.
Eukaryotic chromosomes are composed of which of the following macromolecules?
DNA and proteins
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.
Cells will usually divide if they receive the proper signal at a checkpoint in which phase of the cell cycle?
G1
Cell A has half as much DNA as cells B, C, and D in a mitotically active tissue. Cell A is most likely in...
G1.
Which of the following correctly matches a phase of the cell cycle with its description?
G1: follows cell division
Measurements of the amount of DNA per nucleus were taken on a large number of cells from a growing fungus. The measured DNA levels ranged from 3 to 6 picograms per nucleus. In which stage of the cell cycle did the nucleus contain 6 picograms of DNA?
G2
Which of the following molecules is released by platelets in the vicinity of an injury?
PDGF
Nucleotides can be radiolabeled before they are incorporated into newly synthesized DNA and, therefore, can be assayed to track their incorporation. In a set of experiments, a student-faculty research team used labeled T nucleotides and introduced these into a culture of dividing human cells at specific times. Which of the following question might be answered by using the method described?
What is the length of the S phase of the cell cycle?
A cleavage furrow is _____.
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 the process of cytokinesis
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.
Metaphase is characterized by ________.
alignment of chromosomes on the equator of the cell
Which of these is NOT a carcinogen?
all of the above are carcinogens (UV light, cigarette smoke, testosterone, fat)
Centromeres divide and sister chromatids become full-fledged chromosomes during __________.
anaphase
During which phase of mitosis do the chromatids become chromosomes?
anaphase
Density-dependent inhibition is explained by which of the following processes?
as cells become more numerous, the cell surface proteins of one cell contact the adjoining cells, and they signal each other to stop dividing
After chromosomes condense, the __________ is the region where the identical DNA molecules are most tightly attached to each other.
centromere(s)
What is the name of the microtubule-organizing center found in animal cells as an identifiable structure present during all phases of the cell cycle?
centrosome
The __________ are the organizing centers for microtubules involved in separating chromosomes during mitosis.
centrosome(s)
One difference between cancer cells and normal cells is that cancer cells...
continue to divide even when they are tightly packed together.
What two components constitute an active MPF?
cyclin and a cyclin-dependent kinase
In most eukaryotes, division of the nucleus is followed by __________, when the rest of the cell divides.
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.
__________ is a carcinogen that promotes colon cancer.
fat
Scientists isolate cells in various phases of the cell cycle. They isolate a group of cells that have 1 1/2 times more DNA than G1 phase cells. What is the most likely part of the cell cycle from which these cells were isolated?
in the S phase of the cell cycle
During __________ the cell grows and replicates both its organelles and its chromosomes.
interphase
In dividing cells, most of the cell's growth occurs during __________.
interphase
Nucleoli are present during __________.
interphase
During mitosis, microtubules attach to chromosomes at the __________.
kinetochore(s)
Besides the ability of some cancer cells to over proliferate, which of the following situations might logically result in a tumor?
lack of appropriate cell death
In some organisms, such as certain fungi and algae, cells undergo the cell cycle repeatedly without subsequently undergoing cytokinesis. What would result from this?
large cells containing many nuclei
The __________ is a cell structure consisting of microtubules, which forms during early mitosis and plays a role in cell division.
mitotic spindle(s)
G1 is associated with which of the following cellular events?
normal growth and cell function
What is the best description of the structure of a chromosome in the nucleus of a non-dividing cell?
one long DNA molecule, associated with many proteins
How is plant cell cytokinesis different from animal cell cytokinesis?
plant cells deposit vesicles containing cell wall building blocks on the metaphase plate; animal cells form a cleavage furrow
At which phase of the cell cycle do centrioles begin to move apart in animal cells?
prophase
Chromosomes become visible during __________.
prophase
Spindle fibers attach to kinetochores during __________.
prophase
Which of the following does not occur during mitosis?
replication of the DNA
Which of the following events occurs during interphase of the cell cycle?
replication of the DNA
The mitotic spindle plays a critical role in which of the following processes?
separation of sister chromatids
Movement of the chromosomes during anaphase would be most affected by a drug that prevents which of the following events in mitosis and cell division?
shortening of microtubules
DNA replication produces two identical DNA molecules, called sister __________, which separate during mitosis.
sister chromatid(s)
Cytokinesis often, but not always, accompanies __________.
telophase
During __________ both the contents of the nucleus and the cytoplasm are divided.
the mitotic phase
Taxol is an anticancer drug extracted from the Pacific yew tree. In animal cells, Taxol prevents microtubule depolymerization. Thus, Taxol stops mitosis by interfering with which of the following structures or processes?
the mitotic spindle
During prophase a homologous pair of chromosomes consists of __________.
two chromosomes and four chromatids
