DNA and RNA
Showing posts with label DNA and RNA. Show all posts
Showing posts with label DNA and RNA. Show all posts

Which of the following does not occur during mitosis?

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
E) separation of the spindle poles



Answer: B

The decline of MPF activity at the end of mitosis is due to

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 cyclin.
C) the degradation of cyclin.
D) synthesis of DNA.
E) an increase in the cellʹs volume-to-genome ratio.



Answer: C

One difference between cancer cells and normal cells is that cancer cells

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.
E) are always in the M phase of the cell cycle.


Answer: C

Vinblastine is a standard chemotherapeutic drug used to treat cancer. Because it interferes with the assembly of microtubules, its effectiveness must be related to

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) inhibition of regulatory protein phosphorylation.
C) suppression of cyclin production.
D) myosin denaturation and inhibition of cleavage furrow formation.
E) inhibition of DNA synthesis.



Answer: A

Through a microscope, you can see a cell plate beginning to develop across the middle of a cell and nuclei re-forming on either side of the cell plate. This cell is most likely

Through a microscope, you can see a cell plate beginning to develop across the middle of a cell and nuclei re-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) an animal cell in the S phase of the cell cycle.
D) a bacterial cell dividing.
E) a plant cell in metaphase.



Answer: B

Cells from an advanced malignant tumor most often have very abnormal chromosomes, and often an abnormal total number of chromosomes. Why might this occur?

Cells from an advanced malignant tumor most often have very abnormal chromosomes, and often an abnormal total number of chromosomes. Why might this occur?




A) Cancer cells are no longer density dependent.
B) Cancer cells are no longer anchorage dependent.
C) Chromosomally abnormal cells can still go through cell cycle checkpoints.
D) Chromosomally abnormal cells still have normal metabolism.
E) Transformation introduces new chromosomes into cells.



Answer: C

The research team established similar lymphocyte cultures from a number of human donors, including healthy teenagers of both genders, patients already suffering from long -term bacterial infections, and elderly volunteers. They found that the increase in lymphocyte incorporation after pathogen introduction was slightly lower in some of the women teenagers and significantly lower in each of the elderly persons. They repeated the study with a larger number of samples but got the same results. What might be among their conclusions?

The research team established similar lymphocyte cultures from a number of human donors, including healthy teenagers of both genders, patients already suffering from long -term bacterial infections, and elderly volunteers. They found that the increase in lymphocyte incorporation after pathogen introduction was slightly lower in some of the women teenagers and significantly lower in each of the elderly persons. They repeated the study with a larger number of samples but got the same results. What might be among their conclusions?




A) The young women showed these results because they have poorer nutrition.
B) The elderly personsʹ samples demonstrated their lowered immune responses.
C) The young men had higher response because they are generally healthier.
D) The patient samples should have had the lowest response but did not, so the experiment is invalid.
E) The elderly donor samples represent cells no longer capable of any cell division.



Answer: B

A particular cyclin called cyclin E forms a complex with a cyclin-dependent kinase called Cdk and This complex is important for the progression of the cell from G1 into the S phase of the cell cycle. Which of the following statements is correct?

A particular cyclin called cyclin E forms a complex with a cyclin-dependent kinase called Cdk and This complex is important for the progression of the cell from G1 into the S phase of the cell cycle. Which of the following statements is correct?




A) The amount of cyclin E is greatest during the S phase.
B) The amount of Cdk 2 is greater during G1 compared to the S phase.
C) The amount of cyclin E is highest during G1.
D) The amount of Cdk 2 is greatest during G1.
E) The activity of the cyclin E/Cdk 2 complex is highest during G2.



Answer: C

Which of the following describe(s) cyclin-dependent kinase (Cdk)?

Which of the following describe(s) cyclin-dependent kinase (Cdk)?




A) Cdk is inactive, or ʺturned off,ʺ in the presence of cyclin.
B) Cdk is present throughout the cell cycle.
C) Cdk is an enzyme that attaches phosphate groups to other proteins.
D) Both A and B are true.
E) Both B and C are true.


Answer: E

Which of the following is true concerning cancer cells?

Which of the following is true concerning cancer cells?




A) They do not exhibit density-dependent inhibition when growing in culture.
B) When they stop dividing, they do so at random points in the cell cycle.
C) They are not subject to cell cycle controls.
D) B and C only
E) A, B, and C



Answer: E

Density-dependent inhibition is explained by which of the following?

Density-dependent inhibition is explained by which of the following?




A) As cells become more numerous, they begin to squeeze against each other, restricting their size and ability to produce control factors.

B) As cells become more numerous, the cell surface proteins of one cell contact the adjoining cells and they stop dividing.

C) As cells become more numerous, the protein kinases they produce begin to compete with each other, such that the proteins produced by one cell essentially cancel those produced by its neighbor.

D) As cells become more numerous, more and more of them enter the S phase of the cell cycle.

E) As cells become more numerous, the level of waste products increases, eventually slowing down
metabolism.


Answer: B

A mutation results in a cell that no longer produces a normal protein kinase for the M phase checkpoint. Which of the following would likely be the immediate result of this mutation?

A mutation results in a cell that no longer produces a normal protein kinase for the M phase checkpoint. Which of the following would likely be the immediate result of this mutation?




A) The cell would prematurely enter anaphase.
B) The cell would never leave metaphase.
C) The cell would never enter metaphase.
D) The cell would never enter prophase.
E) The cell would undergo normal mitosis, but fail to enter the next G1 phase.



Answer: E

The MPF protein complex turns itself off by

The MPF protein complex turns itself off by




A) activating a process that destroys cyclin component.
B) activating an enzyme that stimulates cyclin.
C) binding to chromatin.
D) exiting the cell.
E) activating the anaphase-promoting complex.


Answer: A
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