question

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

answer

mitotic phase

question

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

answer

interphase

question

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

answer

32

question

In eukaryotic cells, chromosomes are composed of _____.

answer

DNA and proteins

question

During what phase of the cell cycle does the DNA become replicated?

answer

S

question

What is the difference between a chromatid and a chromosome?

answer

A chromatid is one half of a replicated chromosome, whereas a chromosome consists of DNA wrapped around proteins in a highly organized manner.

question

Which statement is correct concerning the relationship between chromosomes and either genes, chromatin, or sister chromatids?

answer

Each replicated chromosome consists of two sister chromatids.

question

Which answer correctly associates a phase of mitosis with what happens to chromosomes during that phase?

answer

Anaphase: Sister chromatids separate.

question

The microtubule-organizing center found in animal cells is an identifiable structure present during all phases of the cell cycle. Specifically, it is known as the _____.

answer

Centrosome

question

In human and many other eukaryotic species' cells, the nuclear membrane has to disappear to permit _____. a. the disassembly of the nucleolus b. cytokinesis c. the attachment of microtubules to kinetochores d. the splitting of the centrosomes

answer

c. the attachment of microtubules to kinetochores

question

Kinetochore microtubules assist in the process of splitting centromeres by _____. -sliding past each other like actin filaments -using motor proteins to split the centromere at specific arginine residues -creating tension by pulling toward opposite poles -phosphorylating the centromere, thereby changing its conformation

answer

-creating tension by pulling toward opposite poles

question

Mitosis separates chromosomes. Cytoplasm is divided between two daughter cells by _____. -the formation of kinetochores -cloning -binary fission -cytokinesis

answer

-cytokinesis

question

Some cells have several nuclei per cell. How could such multinucleated cells be explained? -The cell underwent repeated mitosis with simultaneous cytokinesis. -The cell had multiple S phases before it entered mitosis. -The cell underwent repeated cytokinesis but no mitosis. -The cell underwent repeated mitosis, but cytokinesis did not occur.

answer

-The cell underwent repeated mitosis, but cytokinesis did not occur

question

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. -The structural proteins of plant cells separate the two cells; in animal cells, a cell membrane separates the two daughter cells. -The contractile filaments found in plant cells are structures composed of carbohydrates; the cleavage furrow in animal cells is composed of contractile phospholipids. -Plant cells divide after metaphase but before anaphase; animal cells divide after anaphase.

answer

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

question

Taxol is an anticancer drug extracted from the Pacific yew tree. In animal cells, Taxol disrupts microtubule formation. Surprisingly, this stops mitosis. Specifically, Taxol must affect _____. anaphase chromatid assembly the S phase of the cell cycle the structure of the mitotic spindle formation of the centrioles

answer

-the structure of the mitotic spindle

question

In which mitotic phase are the sister chromatids separated and pulled to opposite poles? metaphase prophase anaphase telophase

answer

anaphase

question

In which mitotic phase do the chromosomes condense and does the mitotic spindle begin to form? telophase prophase metaphase anaphase

answer

prophase Correct. These are both changes that must occur before the chromosomes can be separated properly.

question

Which answer correctly identifies a cell-cycle checkpoint with a criterion for passing it? See Section 12.3 ( page 264) . Hints Metaphase checkpoint: DNA is undamaged. G2 checkpoint: Chromosomes have replicated successfully. G1 checkpoint: Chromosomes have replicated successfully. S checkpoint: DNA is undamaged.

answer

G2 checkpoint: Chromosomes have replicated successfully. G2 occurs after S and before M phase, so it is advantageous for the cell to have a checkpoint assessing chromosome replication here.

question

Proteins that degrade cyclin are activated by events that MPF initiates. Why is this important for cell-cycle regulation? See Section 12.3 ( page 264) . Hints It sets up an oscillation in cyclin concentration. It results in a Cdk concentration that is more or less constant throughout the cell cycle. It results in the increase in cyclin concentration during interphase. It causes MPF activity to increase during M phase.

answer

It sets up an oscillation in cyclin concentration. Correct. The oscillation in cyclin concentration results in a corresponding oscillation in MPF (cyclin-Cdk complex) activity, which drives the orderly progression between M phase and interphase (see Figure 12.11).

question

What happens if MPF (mitosis-promoting factor) is introduced into immature frog oocytes that are arrested in G2? The cells undergo meiosis. Cell differentiation is triggered. Nothing happens. The cells enter mitosis.

answer

The cells enter mitosis.

question

Once a cell completes mitosis, molecular division triggers must be turned off. What happens to MPF during mitosis? The cyclin component of MPF is degraded. The Cdk component of MPF is degraded and exported from the cell. It is exported from the cell. It is completely degraded.

answer

The cyclin component of MPF is degraded.

question

The M-phase checkpoint ensures that all chromosomes are attached to the mitotic spindle. If this does not happen, cells would most likely be arrested in _____. telophase prometaphase metaphase prophase

answer

metaphase

question

If a cell has accumulated DNA damage, it is unlikely to _____. activate DNA repair mechanisms synthesize cyclin-dependent kinases enter G1 from mitosis pass the G2 checkpoint

answer

pass the G2 checkpoint

question

Regulatory proteins that prevent a cell from entering the S phase under conditions of DNA damage are also known as _____. antibodies cyclins tumor suppressors cyclin-dependent kinases

answer

tumor suppressors

question

Proteins that are involved in the regulation of the cell cycle and that show fluctuations in concentration during the cell cycle are called _____. estrogen receptors cyclins ATPases kinetochores kinases

answer

cyclins

question

Neurons and some other specialized cells divide infrequently because they _____. no longer have active nuclei no longer carry receptors for signal molecules have entered into G0 can no longer bind Cdk to cyclin show a drop in MPF concentration

answer

have entered into G0

question

Which of these is NOT a carcinogen? UV light cigarette smoke testosterone fat all of the above are carcinogens

answer

all of the above

question

_____ is a carcinogen that promotes colon cancer. fat UV light estrogen a virus testosterone

answer

fat

question

Tumor suppressor genes ________. encode proteins that help prevent uncontrolled cell growth often encode proteins that stimulate the cell cycle are cancer-causing genes introduced into cells by viruses are frequently overexpressed in cancerous cells

answer

encode proteins that help

question

BRCA1 and BRCA2 are considered to be tumor suppressor genes because ________. the mutant forms of either one of these prevent breast cancer they block penetration of breast cells by chemical carcinogens the normal genes make estrogen receptors their normal products participate in repair of DNA damage

answer

their normal products participate in repair of DNA damage

question

The cancer-causing forms of the Ras protein are involved in which of the following processes? DNA replication DNA repair cellcell adhesion cell division relaying a signal from a growth-factor receptor

answer

relaying a signal from a growth-factor receptor

question

Forms of the Ras protein found in tumors usually cause which of the following? cell-to-cell adhesion to be nonfunctional excessive cell division DNA replication to be hyperactive DNA replication to stop cell division to cease

answer

excessive cell division

question

What two types of defects does a cancerous cell possess? Cancerous cells possess defects that make proteins required for cell growth active and tumor suppressor genes inactive. Cancerous cells are prevented from dividing and have inhibited growth patterns. Cancerous cells lack the ability to carry out cellular respiration and photosynthesis. Cancerous cells possess defects that make proteins required for cell growth inactive and tumor suppressor genes active.

answer

Cancerous cells possess defects that make proteins required for cell growth active and tumor suppressor genes inactive.

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