Bio 120: chapter 12

Eukaryotic chromosomes are composed of which of the following macromolecules?

DNA and proteins

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

Scientists isolate cells in various phases of the cell cycle. They isolate a group of cells that have 1 1/2 times more DNA than G1 phase cells. What is the most likely part of the cell cycle from which these cells were isolated?

S phase

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

the mitotic phase

What is true of kinetochores?

they are sites at which microtubules attach to chromosomes

What is true of all cancers?

they have escaped normal cell cycle controls

Why is it difficult to observe individual chromosomes with a light microscope during interphase?

they have uncoiled to form long, thin strands

Cytochalasin B is a chemical that disrupts microfilament formation. How would this interfere with cell division?

cleavage

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?

cleavage furrow formation and cytokinesis

In most eukaryotes, division of the nucleus is followed by __________, when the rest of the cell divides.

cytokinesis

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

interphase

In dividing cells, most of the cell's growth occurs during ________.

interphase

Nucleoli are present during _____.

interphase

During mitosis, microtubules attach to chromosomes at the _______.

kinetochore(s)

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

Taxol is an anticancer drug extracted from the Pacific yew tree. In animal cells, Taxol prevents microtubule depolymerization. Thus, Taxol stops mitosis by interfering with which of the following structures or processes?

mitotic spindle

The __________ is a cell structure consisting of microtubules, which forms during early mitosis and plays a role in cell division.

mitotic spindle(s)

How is plant cell cytokinesis different from animal cell cytokinesis?

plant cells deposit vesicles containing cell wall building blocks on the metaphase plate; animal cells form a cleavage furrow

During prophase a homologous pair of chromosomes consists of _____.

two chromosomes and four chromatids

Spindle fibers attach to kinetochores during _____.

prometaphase

Chromosomes become visible during _____.

prophase

What occurs during interphase of the cell cycle?

replication of DNA

Movement of the chromosomes during anaphase would be most affected by a drug that prevents which of the following events in mitosis and cell division?

shortening of microtubules

DNA replication produces two identical DNA molecules, called _________, which separate during mitosis.

sister chromatid(s)

Cytokinesis often, but not always, accompanies _____.

telophase

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

92

A cleavage furrow is _____.

a groove in the plasma membrane between daughter nuclei

Metaphase is characterized by ________.

alignment of chromosomes on the equator of the cell

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

anaphase

During which phase of mitosis do the chromatids become chromosomes?

anaphase

In the cells of many eukaryotic species, the nuclear envelope has to disappear to permit which of the following events in the cell cycle?

attachment of microtubules to kinetochores

How do cancer cells differ from normal cells?

cancer cells may be immortal

After chromosomes condense, the _______ is the region where the identical DNA molecules are most tightly attached to each other.

centromere(s)

The ________ are the organizing centers for microtubules involved in separating chromosomes during mitosis.

centrosome(s)

During interphase, most of the nucleus is filled with a complex of DNA and protein in a dispersed form called ________.

chromatin