biology 101 colombia

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The centromere is a region in which ?

a) chromatids stay attached to one another until anaphase

what is a chromatid

B.> 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

If there are 20 chromatids in a cell, how many centromeres are there?

10

For a newly evolving protist, what would be the advantage of using eukaryote-like cell division rather than binary fission?
A) Binary fission would not allow for the formation of new organisms.

B>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.

at prometaphase of mitosis

B

ONE daughter nucleus at telophase of mitosiS

E

Which term describes two centrosomes arranged at opposite poles of the cell?

prometaphase

Which term describes centrioles beginning to move apart in animal cells?

prophase

Which is the longest of the mitotic stages?

metaphase

Which term 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 be arrested?

metaphase

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

46

) If the cell whose nuclear material is shown in Figure 12.2 continues toward completion of mitosis, which of the following events would occur next?

formation of telophase nuclei

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

Of the following, the best conclusion concerning the difference between the S phases for beta and gamma is that

gamma contains more DNA than beta

The best conclusion concerning delta is that the cells

are actually in the G0 phase.

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

Regarding mitosis and cytokinesis, one difference between higher plants and animals is that in plants

a cell plate begins to form at telophase, whereas in animals a cleavage furrow is initiated at that stage

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

Which of the following 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?

B and C only

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

prevents shortening of microtubules

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 was the nucleus with 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. Those cells would have __________ picograms at the end of the S phase and __________ picograms at the end of G2.

16; 16

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

Mitosis

Imagine looking through a microscope at a squashed onion root tip. The chromosomes of many of the cells are plainly visible. In some cells, replicated chromosomes are aligned along the center (equator) of the cell. These particular cells are in which stage of mitosis?

Metaphase

In order for anaphase to begin, which of the following must occur?

Cohesin must be cleaved enzymatically

Why do chromosomes coil during mitosis?

to allow the chromosomes to move without becoming entangled and breaking

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.

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

Which of the following is a function of those spindle microtubules that do not attach to kinetochores?

maintaining the region of overlap of fibers in the cell's center

Nucleotides can be radiolabeled before they are incorporated into newly forming DNA and can therefore be assayed to track their incorporation. In a set of experiments, a student-faculty research team used labeled T nucleotides and introduced these into the culture of dividing human cells at specific times.

41) Which of the following questions might be answered by such a method?

What is the length of the S phase of the cell cycle?

The research team used the setup to study the incorporation of labeled nucleotides into a culture of lymphocytes and found that the lymphocytes incorporated the labeled nucleotide at a significantly higher level after a pathogen was introduced into the culture. They concluded that

infection causes lymphocytes to divide more rapidly.

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

) Which of the following is released by platelets in the vicinity of an injury?

PDGF

Which is a general term for enzymes that activate or inactivate other proteins by phosphorylating them?

protein kinase

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?

cyclin

Which of the following 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

This is the shortest part of the cell cycle:

M

DNA is replicated at this time of the cell cycle

S

The "restriction point" occurs here:

G1

Nerve and muscle cells are in this phase

G0

The cyclin component of MPF is destroyed toward the end of this phase:

M

In the figure above, mitosis is represented by which number?

IV

G1 is represented by which number(s)?

I and V

Which number represents DNA synthesis?

II

Which number represents the point in the cell cycle during which the chromosomes are replicated?

II

MPF reaches its threshold concentration at the end of this stage.

III

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

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