Mastering Bio Flashcards
Which event does not take place before the start of mitosis? *Organelles proliferate. *The nuclear envelope disintegrates. *DNA is replicated. *The parent cell grows.
The nuclear envelope disintegrates.
True or false? Mitosis takes place during M phase, which is the longest phase of the cell cycle.
False
Which term describes two recently replicated DNA strands that are joined together just before cell division?
Sister chromatids
During which stage of mitosis are chromosomes lined up in the center of the cell?
Metaphase
Which stage of mitosis is characterized by the disintegration of mitotic spindles and the formation of two new nuclear membranes?
Telophase
To which part of the centromere do mitotic spindle fibers attach during prometaphase?
Kinetochore
During which substage of mitosis do sister chromatids break apart and start moving to opposite poles of the cell?
Anaphase
Which term describes centromeres uncoupling, sister chromatids separating, and the two new chromosomes moving to opposite poles of the cell?
anaphase
A cell containing 92 chromatids at metaphase of mitosis would, at its completion, produce two nuclei each containing how many chromosomes?
46
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. Those cells would have __________ picograms at the end of the S phase and __________ picograms at the end of G2.
16; 16
Why do chromosomes coil during mitosis?
to allow the chromosomes to move without becoming entangled and breaking
G1 is represented by which number(s)?
I and IV
Cells that are in a nondividing state are in which phase?
G0
Which is a general term for enzymes that activate or inactivate other proteins by phosphorylating them?
protein kinase
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.
Which of the following is a protein maintained at constant levels throughout the cell cycle that requires cyclin to become catalytically active?
Cdk
A particular cyclin called cyclin E forms a complex with a cyclin-dependent kinase called Cdk 2. This complex is important for the progression of the cell from G 1 into the S phase of the cell cycle. Which of the following statements is correct? *The amount of Cdk 2 is greater during G 1 compared to the S phase. *The amount of Cdk 2 is greatest during G 1 . *The amount of cyclin E is highest during G 1 . * The amount of cyclin E is greatest during the S phase. *The activity of the cyclin E/Cdk 2 complex is highest during G 2 .
The amount of cyclin E is highest during G1.
Besides the ability of some cancer cells to overproliferate, what else could logically result in a tumor?
lack of appropriate cell death
Scientists isolate cells in various phases of the cell cycle. They find a group of cells that have times more DNA than G1 phase cells. The cells of this group are _____.
in the S phase of the cell cycle
A human bone marrow cell, in prophase of mitosis, contains 46 chromosomes. How many chromatids does it contain?
92
Why is it difficult to observe individual chromosomes with a light microscope during interphase?
They have uncoiled to form long, thin strands.
What is true of benign tumors, but not malignant tumors?
They remain confined to their original site
Neurons and some other specialized cells divide infrequently because they _____.
have entered into G0
Cyclin-dependent kinase (Cdk) is _____.
an enzyme that attaches phosphate groups to other proteins
Which of the following is a protein synthesized at specific times during the cell cycle that associates with a kinase to form a catalytically active complex? *Cdk *MPF *PDGF *cyclin
cyclin
Which of the following is a protein maintained at steady levels throughout the cell cycle that requires cyclin to become catalytically active? *PDGF *MPF *cyclin *Cdk
Cdk
In the figure, MPF reaches its highest concentration during this stage.
III
A research team began a study of a cultured cell line. Their preliminary observations showed them that the cell line did not exhibit either density-dependent inhibition or anchorage dependence. What could they conclude right away?
The cells show characteristics of tumors.
For a chemotherapeutic drug to be useful for treating cancer cells, which of the following is most desirable? *It interferes with rapidly dividing cells. *It does not alter metabolically active cells. *It is safe enough to limit all apoptosis. *It interferes with cells entering G 0 .
It interferes with rapidly dividing cells.
Cells from advanced malignant tumors often have very abnormal chromosomes and an abnormal number of chromosomes. What might explain the association between malignant tumors and chromosomal abnormalities?
Cell cycle checkpoints are not in place to stop cells with chromosome abnormalities.
What is the final result of mitosis in a human?
genetically identical somatic cells containing 46 chromosomes
If there are 20 duplicated chromosomes in a cell, how many centromeres are there?
20
True statement about kinetochores?
They are sites at which microtubules attach to chromosomes.
Which of the following correctly matches a phase of the cell cycle with its description? *G 1 : follows cell division *M: duplication of DNA *S: immediately precedes cell division *G 2 : cell division *All of the above are correctly matched.
G1: follows cell division
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
Cytochalasin B is a chemical that disrupts microfilament formation. How would this interfere with cell division?
cleavage
In human and many other eukaryotic species’ cells, the nuclear membrane has to disappear to permit _____.
the attachment of microtubules to kinetochores
At which phase are centrioles beginning to move apart in animal cells?
prophase
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
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
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 would be found at the end of S and the end of G2?
16; 16
The beginning of anaphase is indicated by which of the following? *Chromatids lose their kinetochores. *Spindle microtubules begin to polymerize. *Cohesin is cleaved enzymatically. *Cohesin attaches the sister chromatids to each other.
Cohesin is cleaved enzymatically.
During which phase of mitosis do the chromatids become chromosomes?
anaphase
What is the correct chromosomal condition at prometaphase of mitosis?
B
What is the correct chromosomal condition for one daughter nucleus at telophase of mitosis?
E
If the cell whose nuclear material is shown in the accompanying figure continues toward completion of mitosis, which of the following events would occur next?
formation of telophase nuclei
In the figure, which number represents DNA synthesis?
II
In the figure, at which of the numbered regions would you expect to find cells at metaphase?
III only
Centromeres split and sister chromatids migrate to opposite poles in meiosis _____.
anaphase II
The DNA content of a diploid cell in the G1 phase of the cell cycle is x. The DNA content of a single cell at metaphase of meiosis II would be
x
Homologous pairs of chromosomes align opposite of each other at the equator of a cell during _____.
meiosis metaphase I
Which diagram represents anaphase I of meiosis?
I
When we first see chiasmata under a microscope, we know that _____.
prophase I is occurring
After telophase I of meiosis, the chromosomal makeup of each daughter cell is _____.
haploid, and the chromosomes are each composed of two chromatids
What is crossing over?
the exchange of homologous portions of nonsister chromatids
What is karyotype?
organized images of a cells chromosomes
Quaking aspen can send out underground stems for asexual reproduction. Sexual reproduction is not as common, but when it does happen, the haploid gametes have 19 chromosomes. How many chromosomes are in the cells of the underground stems?
38
If meiosis produces haploid cells, how is the diploid number restored for those organisms that spend most of their life cycle in the diploid state?
fertilization
In a human karyotype, chromosomes are arranged in 23 pairs. If we choose one of these pairs, such as pair 14, what do the two chromosomes of the pair have in common?
length, centromere position, staining pattern, and traits coded for by their genes
A triploid cell contains sets of three homologous chromosomes. If a cell of a usually diploid species with 42 chromosomes per cell is triploid, this cell would be expected to have which of the following? *21 chromosome pairs and 21 unique chromosomes *63 chromosomes in pairs *63 chromosomes, each with three chromatids *63 chromosomes in 21 sets of 3
63 chromosomes in 21 sets of 3
Which of the following is true of a species that has a chromosome number of 2 n = 16? *A gamete from this species has four chromosomes. *Each diploid cell has eight homologous pairs. *The species is diploid with 32 chromosomes per cell. *The species has 16 sets of chromosomes per cell.
Each diploid cell has eight homologous pairs.
How are sister chromatids and homologous chromosomes different from each other?
Homologous chromosomes contain the same gene loci but may have different alleles of a particular gene. Sister chromatids are identical copies of each other produced during DNA replication.
Define a genome
the complete set of an organism’s genes and other DNA sequences
Which of the following occurs during meiosis but not during mitosis? *Chromosomes migrate to opposite poles. *Synapsis occurs. *Chromosomes align at the metaphase plate. *Chromosomes condense. *A spindle apparatus forms.
Synapsis occurs
Which of the life cycles is typical for animals?
I only
A given organism has 23 pairs of homologs in its karyotype. Therefore, we can conclude that it must _____.
have gametes with 23 chromosomes
If a cell has completed meiosis I and is just beginning meiosis II, which of the following is an appropriate description of its contents? *It has half the chromosomes but twice the DNA of the originating cell. *It has one-fourth the DNA and one-half the chromosomes as the originating cell. *It has half the amount of DNA as the cell that began meiosis. *It is identical in content to another cell formed from the same meiosis I event.
It has half the amount of DNA as the cell that began meiosis.
What happens at the conclusion of meiosis 1?
Homologous chromosomes of a pair are separated from each other.
Sister chromatids separate from each other during _____.
mitosis and meiosis II
Which of the following occurs in meiosis but not in mitosis? *alignment of chromosomes at the equator *condensation of chromosomes *chromosome replication *synapsis of chromosomes
synapsis of chromosomes
Which diagram represents anaphase II of meiosis?
V
Which sample of DNA might be from a nerve cell arrested in G0 of the cell cycle?
I
Which sample might represent an animal cell in the G2 phase of the cell cycle?
II
Which sample might represent a zygote?
I
What is a major difference between meiosis II and mitosis in animals?
Meiosis II occurs only in haploid cells, while mitosis occurs only in diploid cells.
What is a major difference between mitosis and meiosis I in a diploid organism?
Sister chromatids separate in mitosis, while homologous pairs of chromosomes separate in meiosis I.
Crossing over normally takes place during which of the following processes?
meiosis 1
