CH 9 The Cell Cycle HW

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

Which is the first checkpoint in the cell cycle where a cell will be caused to exit the cycle if this point is not passed?

G1

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

Which of the following is true of benign tumors, but not malignant tumors?

They remain confined to their original site

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 formation of the mitotic spindle.

During _____ both the contents of the nucleus and the cytoplasm are divided.

the mitotic phase

Which of the following is true of kinetochores?

they are sites at which microtubules attach to chromosomes.

Humans produce skin cells by mitosis and gametes by meiosis. The nuclei of skin cells produced by mitosis will have

twice as much DNA as the nuclei of gametes produced by meiosis.

During _____ the cell grows and replicates both its organelles and its chromosomes.

interphase

Nucleoli are present during _____.

interphase

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

Which of these phases encompasses all of the stages of mitosis but no other events?

mitosis

During prophase a homologous pair of chromosomes consists of _____.

two chromosomes and four chromatids

Spindle fibers attach to kinetochores during _____.

prometaphase

At which phase are centrioles beginning to move apart in animal cells?

prophase

Chromosomes become visible during _____.

prophase

Cytokinesis often, but not always, accompanies _____.

telophase

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

10

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

10

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

A human bone marrow cell, in prophase of mitosis, contains 46 chromosomes. How many chromatids does it contain?

92

What is a cleavage furrow?

a groove in the plasma membrane between daughter nuclei

Centromeres divide and sister chromatids become full-fledged chromosomes during _____.

anaphase

In eukaryotic cells, chromosomes are composed of DNA

and proteins.

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

centrosome