AP Biology Chapter 12

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The centromere is a region in which

chromatids remain attached to one another until anaphase.

What is a chromatid?

a replicate chromosome

Starting with a fertilized egg (zygote), a series of five cell divisions would produce an early embryo with how many cells?

32

For a newly evolving protist, what would be the advantage of using eukaryote-like cell division rather than binary fission?

Cell division would allow for the orderly and efficient segregation of multiple linear chromosomes.

How do the daughter cells at the end of mitosis and cytokinesis compare with their parent cell when it was in G1 of the cell cycle?

The daughter cells have the same number of chromosomes and the same amount of DNA.

What phase describes two centrosomes arranged at opposite
poles of the cell?

prometaphase

What stage describes centrioles beginning to move apart in animal cells?

prophase

Which is the longest of the mitotic stages?

metaphase

What stage describes centromeres uncoupling, sister
chromatids separating, and the two new chromosomes moving to opposite poles of the cell?

anaphase

If cells in the process of dividing are subjected to colchicine, a drug that interferes with the functioning of the spindle apparatus, at which stage will mitosis stop?

metaphase

A cell containing 92 chromatids at metaphase of mitosis would, at its completion, produce two nuclei each containing how many chromosomes?

46

If there are 20 centromeres in a cell at anaphase, how many chromosomes are there in each daughter cell following cytokinesis?

20

If there are 20 chromatids in a cell at metaphase, how many chromosomes are there in each daughter cell following cytokinesis?

10

Where do the microtubules of the spindle originate during mitosis in both plant and animal cells?

centrosome

If a cell has 8 chromosomes at metaphase of mitosis, how many chromosomes will it have during anaphase?

16

Cytokinesis usually, but not always, follows mitosis. If a cell completed mitosis but not cytokinesis, the result would be a cell with

two nuclei.

The formation of a cell plate is beginning across the middle of a cell and nuclei are re-forming at opposite ends of the cell. What kind of cell is this?

a plant cell undergoing cytokinesis

Taxol is an anticancer drug extracted from the Pacific yew tree. In animal cells, taxol disrupts microtubule formation by binding to microtubules and accelerating their assembly from the protein precursor, tubulin. Surprisingly, this stops mitosis. Specifically, taxol must affect

the fibers of the mitotic spindle.

What are primarily responsible for cytokinesis in plant cells?

Golgi-derived vesicles

Chromosomes first become visible during which phase of mitosis?

prophase

During which phases of mitosis are chromosomes composed of two chromatids?

from G2 of interphase through metaphase

In which group of eukaryotic organisms does the nuclear envelope remain intact during mitosis?
A) seedless plants
B) dinoflagellates
C) diatoms
D) B and C only
E) A, B, and C

B and C only

Movement of the chromosomes during anaphase would be most affected by a drug that

prevents shortening of microtubules.

The somatic cells derived from a single-celled zygote divide by which process?

mitosis

In order for anaphase to begin, what must occur?

Cohesin must be cleaved enzymatically.

Why do chromosomes coil during mitosis?

to allow the chromosomes to move without becoming entangled and breaking

Several organisms, primarily Protists, have what are called intermediate mitotic organization. These Protists are intermediate in what sense?

They maintain a nuclear envelope during division.

What is the most probable hypothesis about these intermediate forms of cell division?

They show some of the evolutionary steps toward complete mitosis but not all.

Which of the following best describes how chromosomes move toward the poles of the spindle during mitosis?
A) The chromosomes are "reeled in" by the contraction of spindle microtubules.
B) Motor proteins of the kinetochores move the chromosomes along the spindle microtubules.
C) Non-kinetochore spindle fibers serve to push chromosomes in the direction of the poles.
D) both A and B
E) A, B, and C

Motor proteins of the kinetochores move the chromosomes along the spindle microtubules.

If mammalian cells receive a go-ahead signal at the G1 checkpoint, they will

complete the cycle and divide.

Cells that are in a nondividing state are in which phase?

G0

What causes the decrease in the amount of cyclin at a specific point in the cell cycle?

its destruction by a process initiated by the activity of its complex with a cyclin

What is released by platelets in the
vicinity of an injury?

PDGF

What is the general term for enzymes that activate or inactivate other proteins by phosphorylating them?

protein kinase

Fibroblasts have receptors for this substance on their
plasma membranes.

PDGF

What is a protein synthesized at specific times during the cell cycle that associates with a kinase to form a catalytically active complex?

cyclin

What is a protein maintained at constant levels throughout the cell cycle that requires cyclin to become catalytically active?

Cdk

Which of the following triggers the cell's passage past the G2 checkpoint into mitosis?

MPF

What is the shortest part of the cell cycle?

M phase

In what part of the cell cycle is DNA replicated?

S phase

In what part of the cell cycle is the "restriction point"?

G1 phase

In what part of the cell cycle are the nerve and muscle cells?

G0 phase

Towards the end of which phase of the cell cycle is the cyclin component of MPF destroyed?

M phase

An enzyme that attaches a phosphate group to another molecule is called a

kinase.

Proteins that are involved in the regulation of the cell cycle, and that show fluctuations in concentration during the cell cycle, are called

cyclins.

The MPF protein complex turns itself off by

activating a process that destroys cyclin component.

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

The cell would undergo normal mitosis, but fail to enter the next G1 phase.

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

A, B, and C

Which of the following describe(s) cyclin-dependent kinase (Cdk)?
A) Cdk is inactive, or "turned off," 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.

Both B and C are true.

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 G1 into the S phase of the cell cycle. What statements is correct?

The amount of cyclin E is highest during G1.

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

Chromosomally abnormal cells can still go through cell cycle checkpoints.

Besides the ability of some cancer cells to overproliferate, what else could logically result in a tumor?

lack of appropriate cell death

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

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.

The drug cytochalasin B blocks the function of actin. Which of the following aspects of the cell cycle would be most disrupted by cytochalasin B?

cleavage furrow formation

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