chapter 12 study guide
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? (A) 0 (B) 7 (C) 14 (D) 28 (E) None of the listed responses are correct.
(A) 0 By telophase, the chromatids have separated and the individual units of DNA are arriving at the poles. There are no chromatids at this point. They are not considered chromatids because they are not attached at the centromere anymore.
A cell contains 40 chromatids at the beginning of mitosis. How many chromosomes will it contain at the completion of cytokinesis? (A) 20 (B) 40 (C) 160 (D) 80 (E) 5 (F) 10
(A) 20 If a cell contains 40 chromatids at the beginning of mitosis, it will have 80 chromosomes to begin with. By the end of cytokinesis, it will have 40 chromosomes. In turn, that means that there will only be 20 chromatids.
How many chromatids does a human somatic cell contain after interphase and just prior to mitosis? (A) 92 (B) 69 (C) 22 (D) 184 (E) 23 (F) 46
(A) 92 After interphase and before mitosis, a human somatic cell would have 92 chromatids. This is because a human somatic cell at the time would have 46 chromosomes (23 pairs) * 2 (chromatids) = 92 sister chromatids.
In the cells of some organisms, mitosis occurs without cytokinesis. This will result in: (A) cells with more than one nucleus. (B) cells that are unusually small. (C) cells lacking nuclei. (D) cell cycles lacking an S phase
(A) Cells with more than one nucleus. Without cytokinesis, the two daughter cells are "stuck" together => ends up with two nuclei.
Vinblastine is a standard chemotherapeutic drug used to treat cancer. Because it interferes with the assembly of microtubules, its effectiveness must be related to: (A) disruption of mitotic spindle formation. (B) suppression of cyclin production. (C) myosin denaturation and inhibition of cleavage furrow formation. (D) inhibition of DNA synthesis
(A) Disruption of mitotic spindle formation. Microtubules and centrosomes make up the mitotic spindle; if there was a drug that interfered with microtubules, it would affect the spindle.
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? (A) 50 units (B) 100 units (C) between 50 and 100 units (D) 200 units (E) 400 units
(B) 100 units G2 follows S; in S phase, DNA is replicated. Cell division is very exact. The amount of DNA would never be indicated by a range.
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? (A) 15 (B) 30 (C) 45 (D) 60 (E) 120
(B) 30 At the completion of the cell cycle, each daughter cell will have the same chromosomal complement as the parent cell. At the beginning of mitosis, there are 60 chromatids = equivalent to = 30 chromosomes. During mitosis, the chromosomes will double (60 chromosomes) and will divide to 30 chromosomes for each daughter cell.
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) an animal cell in the process of cytokinesis. (B) a plant cell in the process of cytokinesis. (C) a bacterial cell dividing. (D) a plant cell in metaphase
(B) A plant cell in the process of cytokinesis. In plant cells, cytokinesis does not form a cleavage furrow like it does in animal plants. Instead, it forms cell plates and cell walls.
Which event or events occur during anaphase? (A) A spindle made of microtubules is present. (B) All of the listed responses are correct. (C) Identical chromatids move to opposite poles. (D) The centromeres divide. (E) The centrioles are at opposite poles.
(B) All of the listed responses are correct. This is the definition of what happens in anaphase.
Which of the following statements correctly describes the difference(s) between mitosis and binary fission? (A) There are no differences between binary fission and mitosis. (B) Binary fission involves the replication and division of a single chromosome, whereas mitosis involves the division of multiple, replicated chromosomes. (C) A cell plate forms across the middle of two cells dividing by binary fission, but this does not occur in mitosis. (D) Binary fission involves the replication and division of multiple chromosomes, whereas mitosis involves the replication and division of a single chromosome. (E) Binary fission in bacteria is completed by microtubules, but mitosis does not involve these structures. (F) None of the listed responses is correct.
(B) Binary fission involves the replication and division of a single chromosome, whereas mitosis involves the division of multiple, replicated chromosomes. Binary fission only deals with one chromosomes with two origins of replications. It does not replicate multiple chromosomes.
When a cell in S phase is fused with a cell in G1, __________. (A) the two nuclei fuse and additional division is arrested (B) DNA synthesis begins immediately in the original G1 nucleus (C) the original G1 cell will divide immediately (D) the replication of DNA occurring in the original S nucleus is terminated (E) the chromosomes of the original G1 nucleus condense in preparation for mitosis
(B) DNA synthesis begins immediately in the original G1 nucleus Cytoplasmic signals can participate in the regulation of the cell cycle. When fused, usually the original cell takes precedence.
Chromatids are __________. (A) composed of RNA (B) identical copies of each other if they are part of the same duplicated chromosome (C) held together by the centrioles (D) found only in aberrant chromosomes (E) the bacterial equivalent of eukaryotic chromosomes
(B) Identical copies of each other if they are part of the same duplicated chromosome. Each duplicated chromosome consists of two identical sister chromatids. It is composed of DNA and proteins.
Which of the following does not occur during mitosis? (A) condensation of the chromosomes (B) replication of the DNA (C) separation of sister chromatids (D) spindle formation
(B) Replication of the DNA. Replication of DNA takes place in the S phase. (G1 and G2, the G phases, indicate "G"rowing).
The decline of MPF activity at the end of mitosis is due to: (A) the destruction of the protein kinase Cdk. (B) decreased synthesis of Cdk. (C) the degradation of cyclin. (D) the accumulation of cyclin.
(B) The degradation of cyclin. MPF is a cyclin-Cdk complex that stimulates the M phase to happen. MPF activity corresponds to levels of cyclin concentration. If cyclin conc. high, MPF activity is high. If cyclin conc. low, MPF activity is low. Cyclin level rises during S and G2 phases, but lowers immediately at M phase.
One difference between cancer cells and normal cells is that cancer cells: (A) are unable to synthesize DNA. (B) are arrested at the S phase of the cell cycle. (C) continue to divide even when they are tightly packed together. (D) cannot function properly because they are affected by density-dependent inhibition.
(C) Continue to divide even when they are tightly packed together. Cancer cells continue to divide, ignoring signals that "command" them to stop.
You would be UNLIKELY to see which of the following human cells dividing? (A) Cancer cell (B) Skin cell (C) Nerve cell (D) cell from embryo (E) All of these cell types are equally unlikely to divide at any given time.
(C) Nerve cell. Cancer cells are characterized by unable to prevent division. Skin cells are replaced all the time. Cells from embryos must divide in order to grow. Nerve cells enter G0 phase after reaching maturity.
If a human somatic cell is just about to divide, it has __________ chromatids. (A) 0 (B) 23 (C) 46 (D) 92
(D) 92 Human somatic cells have 46 chromosomes, which contains 92 chromatids.
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? (A) 23 (B) 46 (C) 92 (D) 94 (E) 98
(D) 94 If an individual has Down syndrome, it has an extra chromosome (meaning it has 47 chromosomes in total). As a result, they would have 94 chromatids.
Which of the following is FALSE regarding sister chromatids? (A) Sister chromatids form in the S-phase stage of the cell cycle. (B) Sister chromatids are created when DNA is replicated. (C) Sister chromatids are separated during mitosis. (D) Both of the sister chromatids end up in the same daughter cell after cytokinesis has occurred. (E) Sister chromatids are attached to one another at the centromere.
(D) Both of the sister chromatids end up in the same daughter cell after cytokinesis has occurred. On the metaphase plate, the sister chromatids divide and get separated into different daughter cells. Sister chromatids are formed in the S-phase, which is when DNA replication occurs.
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? (A) spindle formation (B) spindle attachment to kinetochores (C) cell elongation during anaphase (D) cleavage furrow formation and cytokinesis
(D) Cleavage furrow formation and cytokinesis. This is because on the CYTOPLASMIC side of the furrow is a contractile ring of ACTIN MICROFILAMENTS. This drug will inhibit the function of action, making the contractile ring unable to form the cleavage furrow.
Cell A has half as much DNA as cells B, C, and D in a mitotically active tissue. Cell A is most likely in: (A) G1. (B) G2. (C) prophase. (D) metaphase
(D) G1. This is the "first" steps towards mitosis. In G1, the cell begins to grow.
During what phase in the cell cycle would you find the most DNA per cell? (A) G1 (B) S (C) G0 (D) G2 (E) S1
(D) G2 Chromosomes are duplicated during the S phase, but are not finishing duplicating until G2 (where it has the most DNA).
In a human skin cell that is going through the cell cycle, when do the centrosomes separate? (A) anaphase (B) G2 phase (C) S phase (D) prophase (E) metaphase
(D) 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.
Which of the following phases of mitosis is essentially the opposite of prometaphase in terms of the nuclear envelope? (A) Interphase (B) Anaphase (C) Metaphase (D) Telophase (E) S phase
(D) Telophase. Prometaphase is just when the nuclear envelope is about to disappear (fragment). The opposite of that is telophase, when the nuclear envelope reappears again.
A cell entering the cell cycle with 32 chromosomes will produce two daughter cells, each with __________. (A) 16 chromosomes (B) 64 chromosomes (C) 32 pairs of chromosomes (D) 64 pairs of chromosomes (E) none of the listed numbers of chromosomes
(E) None of the listed numbers of chromosomes. There would be 32 chromosomes present in each of the daughter cells. 32 at the beginning of the cell cycle => 64 after duplication => split into 32 chromosomes for each daughter cell.
How does the process of mitosis differ between most eukaryotes and other eukaryotes such as diatoms and dinoflagellates? (A) Sister chromatids are not separated during mitosis in diatoms and dinoflagellates. (B) The nuclear envelope remains intact in most eukaryotes but fragments in diatoms and dinoflagellates. (C) The chromosomes are not duplicated prior to mitosis in diatoms and dinoflagellates. (D) Microtubules do not facilitate the movement of chromosomes in diatoms and dinoflagellates. (E) fragments in most eukaryotes but remains intact in diatoms and dinoflagellates.
(E) The nuclear envelope fragments in most eukaryotes but remains intact in diatoms and dinoflagellates (similar to the bacteria in binary fission).
