Bio150-ch12

Which statement provides the best description of the interphase portion of the cell cycle?

During interphase, a cell is metabolically active.

Chromosomes become visible during _____.

During prophase, the chromatin fibers become discrete chromosomes.

Cells will usually divide if they receive the proper signal at a checkpoint in which phase of the cell cycle?

G1, in mammalian cells, this checkpoint is termed the restriction point.

Which of the following correctly matches a phase of the cell cycle with its description?

G1- immediately follows cell division. After mitosis and cytokinesis, the newly formed daughter cells enter the G1 phase.

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

Are sister chromatids present in all or part of this phase?

S G2 Begining of M propase early anaphase

The cell cycle control system of cancer cells differ from those of normal cells. Select the best explanation for this fact.

The underlying basis of cancer is almost always a change in one of more genes that alters the function of their protein products, resulting in faulty cell cycle control.

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

mitotic spindles

What is the best description of the structure of a chromosome in the nucleus of a non-dividing cell?

one long DNA molecule associated with many proteins

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

64

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

92, mitosis follows the duplication of the cell's DNA

Which of the following properties is associated with a cyclin-dependent kinase?

A Cdk is an enzyme that attaches phosphate groups to other proteins.

Spindle fibers attach to kinetochores during _____.

Attachment of spindle fibers to kinetochores is one of the events of prometaphase.

In most eukaryotic, division of the nucleus is followed by _____ , well the rest of the cell divides.

Cytokinesis

Eukaryotic chromosomes are composed of which of the following macromolecules?

DNA and proteins

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

During anaphase, sister chromatids separate and daughter chromosomes migrate to opposite poles.

In metaphase, the kinetochore microtubules have attached each pair of sister chromatids, and the nonkinetochore microtubules overlap extensively at the metaphase plate.

During anaphase, the kinetochore microtubules shorten as the chromosomes move towards the poles of the cell. At the same time, nonkinetochore microtubules lengthen and push past each other, elongating the cell.

If a eukaryotic cell is in the G1 phase of the cell cycle, which statement about the cell's chromosomes must be correct?

Each chromosome is made of a complex of DNA and associated proteins.

______ is a carcinogen member that promotes colon cancer.

Fat, a diet high in fat increases the risk of both colon and breast cancer.

Call A has as much DNA as cells B,C, and D in mitotically active tissue. Cell A is most likely in ___.

G1

Is the DNA condensed in all or part of this phase?

G1: no S: no G2: no beginning of M: yes end of M: yes

Does the cell contain twice as much DNA in this phase as it did in the G1 phase?

G1: no S: yes G2: yes beginning of M: yes end of M: yes

Nucleoli are present during _____.

Nucleoli are present during interphase.

What effect does phosphorylating a protein have on that protein?

Phosphorylation changes the shape of the protein, most often activating it.

The mitotic spindle is the machinery that guides the separation of chromosomes in anaphase.

Prior to metaphase, the mitotic spindle is constructed by lengthening microtubules that extends from each centrosome.

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

The Mitotic Phase: The Mitotic Phase encompasses both Mitosis and Cytokinesis!

Which of the following is true kinetochores?

They are sites at which microtubules attach to chromosomes.

Why do neurons and some other specialized cells divide infrequently?

They have entered into G0.

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.

Why do some species employ both mitosis and meiosis, whereas other species use only mitosis?

They need both if they are producing plant gametes.

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

They remain confined to their original site.

Through a microscope, you can see a cell plate beginning to develop across the middle of a cell and nuclei forming on either side of the cell plate. This cell is most likely

a plant cell in the process of cytokinesis.

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

centromeres

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

centromeres

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

chromatin

Which of these is NOT a carcinogen?

cigarette smoke, fat, UV light, testosterone, all of the above are carcinogens -all of these substances can cause cancer

One difference between cancer cells and normal cells is that cancer cells _____.

continue to divide even when they are tightly packed together.

What two components constitute an active MPF?

cyclin and a cyclin-dependent kinase

During telophase, the nonkinetochore microtubules _______.

disassemble

Vinblastine is a standard chemotherapeutic drug used to treat cancer. Because it interferes with the assembly of microtubules, its effectiveness must be related to

disruption of mitotic spindle formation.

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

e. mitosis

During mitosis, microtubules attach to chromosomes at the ______.

kinetochores

In some organisms, such as certain fungi and algae, the cells undergo the cell cycle repeatedly without subsequently undergoing cytokinesis. What would result from this?

large cells containing many nuclei

During prophase, the microtubules of the mitotic spindle ______.

lengthen

During anaphase, the nonkinetochore microtubules _______ and move past each other and a the kinetochore microtubules ______.

lengthen, shorten

Which of the following does not occur during mitosis?

replication of DNA

DNA replication produces two identical DNA molecules, called

sister chromatids, which separates during mitosis.

Cytokinesis often, but not always, accompanies _____.

telophase

The decline of MPF activity at the end of mitosis is due to ____.

the degradation of cyclin.