Ch. 9- The Cell Cycle

How can a protein outside the cell cause events to happen inside the cell?

a) A protein outside the cell can cause the H+ ion concentration outside the cell to be higher, which allows substances to pass into the cell and transduce a signal.

b) A protein can pass through the membrane and into the cell, causing signaling inside the cell.

c) A protein outside the cell can bind to a receptor protein on the cell surface, causing it to change shape and sending a signal inside the cell.

d) A protein outside the cell can phosphorylate a protein inside the cell, which transduces a signal and causes a response.

c

What effect does phosphorylating a protein have on that

protein?

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

b) Phosphorylation may have no effect at all on the protein.

c) Phosphorylation adds energy to the protein, allowing it to form ATP from ADP and Pi.

d) Phosphorylation adds one or more phosphorus atoms to the protein, allowing it to perform a particular function.

a

Beginning with a fertilized egg (zygote), how many cells would be present in an embryo following a series of six cell

divisions?

a) 6

b) 12

c) 24

d) 64

e) 128

d

A cell in G2 of the cell division cycle contains 16 chromatids. How many centromeres are present in this cell?

a) 8

b) 16

c) 32

d) 40

e) 64

b

Which of the following components make(s) up eukaryotic

chromatin?

a) DNA and carbohydrates

b) DNA and RNA

c) condensed DNA only

d) DNA and proteins

e) DNA and ribosomes

d

What will be the result if a eukaryotic cell completes mitosis but does not undergo cytokinesis?

a) one cell with two nuclei, each containing half of the genetic material of the parent cell

b) one cell with two nuclei, each identical to the nucleus of the parent cell

c) two cells, each cell with half of the genetic material of the parent cell

d) two cells, one cell containing two nuclei and a second cell without a nucleus

e) one cell with one nucleus containing half of the genetic material of the parent cell

b

Following DNA replication, each eukaryotic chromosome consists of two identical DNA molecules known as

a) sister cohesins

b) sister chromatids

c) sister chromatins

d) daughter chromosomes

b

Nucleoli are present during

_____.

a) anaphase

b) prophase

c) prometaphase

d) metaphase

e) interphase

e

Cytokinesis often, but not always, accompanies

_____.

a) metaphase

b) interphase

c) prometaphase

d) anaphase

e) telophase

e

Chromosomes become visible during _____.

a) prometaphase

b) anaphase

c) metaphase

d) prophase

e) interphase

d

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

a) anaphase

b) prometaphase

c) interphase

d) metaphase

e) telophase

a

Spindle fibers attach to kinetochores during _____.

a) interphase

b) anaphase

c) prometaphase

d) telophase

e) metaphase

c

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

a) G2

b) S

c) the mitotic phase

d) G1

e) mitosis

c

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

a) G1

b) S

c) interphase

d) cytokinesis

e) mitosis

c

If there are 32 centromeres in a cell at anaphase of mitosis, how many chromosomes are there in each daughter cell following cytokinesis?

a) 8

b) 16

c) 32

d) 64

b

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

a) centriole

b) centrosome

c) chromatid

d) centromere

e) kinetochore

b

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

processes?

a) shortening of microtubules

b) elongation of microtubules

c) nuclear envelope breakdown

d) formation of a cleavage furrow

e) cell wall formation

a

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 would the nucleus contain 6 picograms of DNA?

a) S

b) G0

c) G2

d) G1

c

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 of DNA would be found in a nucleus at the end of G1 and the end of G2?

a) 16; 8

b) 8; 8

c) 4; 8

d) 8; 16

d

A group of cells is assayed for DNA content immediately before beginning mitosis and is found to have an average of 20 picograms of DNA per nucleus. How many picograms of DNA would be found in a cell nucleus following completion of mitosis and cytokinesis?

a) 5

b) 10

c) 20

d) 40

b

At which phase of mitosis do the sister chromatids become daughter chromosomes?

a) cytokinesis

b) anaphase

c) prometaphase

d) metaphase

e) prophase

b

Which statement below best describes a cleavage

furrow?

a) the metaphase plate where chromosomes attach to the spindle

b) a groove in the plasma membrane between daughter nuclei

c) a ring of vesicles forming a cell plate

d) an indentation between daughter prokaryotic cells

b

A plant-derived protein known as colchicine can be used to poison cells by blocking the formation of the mitotic spindle. Which statement below best summarizes the predicted effect of adding colchicine to a sample of cells in G2?

a) Chromosomes would condense but fail to align at the metaphase plate, and the cell cycle would arrest at this point.

b) The cells would immediately die.

c) The nuclear membrane would break down, but chromosomes would fail to condense and the cell cycle would arrest in early prophase.

d) The cells would be unable to begin M, and the cell cycle would arrest in G2.

a

When a cell is in late anaphase of mitosis, which of the following may be observed?

a) chromosomes clustered tightly at the center of the dividing cell

b) individual chromatids beginning to separate from one another

c) decondensing chromosomes clustered at the poles

d) nuclear envelopes forming at the poles

e) a clear area in the center of the dividing cell

e

Which of the following events is associated with prophase of mitosis in animal cells?

a) cleavage of cohesins by separase

b) alignment of the chromosomes at the equator of the cell

c) depolymerization of spindle microtubules

d) movement of the centrioles toward opposite sides of the cell

e) movement of daughter chromosomes toward opposite sides of the cell

d

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) a bacterial cell dividing

b) an animal cell in the process of cytokinesis

c) a plant cell in metaphase

d) a plant cell in the process of cytokinesis

d

In the cells of some organisms, mitosis occurs WITHOUT cytokinesis. This will result in __________.

a) cells that are unusually small

b) cells lacking nuclei

c) cell cycles lacking an S phase

d) cells with more than one nucleus

d

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

a) prophase

b) G1

c) G2

d) metaphase

b

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

a) Sister chromatids do not pair up until division starts.

b) They leave the nucleus and are dispersed to other parts of the cell.

c) Interphase chromosomes are long, thin strands unlike the condensed chromosomes visible in mitosis.

d) The spindle must move them to the metaphase plate before they become visible.

e) The DNA has not been replicated yet.

c

Which of the following is true of kinetochores?

a) They are the primary centromere structures that maintain the attachment of the sister chromatids prior to mitosis.

b) They interdigitate at the cell's equator and then move apart, causing the cell to elongate.

c) They are sites at which microtubules attach to chromosomes.

d) They are located at the center of the centrosome; their function is to organize tubulin into elongated bundles called spindle fibers.

e) They attach to the ring of actin along the cytoplasmic surface of the plasma membrane, causing the actin to contract to form the cleavage furrow.

c

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

a) S: immediately precedes cell division

b) G2: cell division

c) G1: follows cell division

d) All of the listed responses are correctly matched.

e) M: duplication of DNA

c

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

this?

a) large cells containing many nuclei

b) division of the organism into many cells, most lacking nuclei

c) a rapid rate of gamete production

d) inability to duplicate DNA

e) a decrease in chromosome number

a

Which is the first checkpoint in the cell cycle that will cause a cell to exit the cycle if this point is not passed?

a) S

b) G0

c)G2

d) M

e) G1

e

The cell cycle is regulated at the molecular level by a set of proteins known as

a) cohesins.

b) separase proteins.

c) cyclins.

d) ATPases.

c

Density-dependent inhibition is explained by which of the following statements?

a) As cells become more numerous, the cell surface proteins of adjacent cells bind to each other and send signals that inhibit cell division.

b) As cells become more numerous, the protein kinases they produce begin to compete with each other, such that the proteins produced by one cell essentially cancel those produced by its neighbor.

c) As cells become more numerous, they begin to squeeze against each other, restricting their size and ability to produce growth factors.

d) As cells become more numerous, the level of waste products increases, eventually slowing down metabolism.

a

Which of the following characteristics is associated with cancer cells?

a) They must be attached to a substrate to divide in culture.

b) They stop dividing in culture when growth factors are depleted.

c) They evade the normal controls that trigger programmed cell death.

d) They exhibit density-dependent inhibition when growing in culture.

c

Which alteration in cellular behavior listed below would be most likely to result in tumor formation?

a) enhanced anchorage dependence

b) inability to form spindles

c) changes in the order of cell cycle stages

d) lack of appropriate cell death

d

Why do most cells in the human body divide

infrequently?

a) They have exited the cell cycle and entered G0.

b) They have defective microtubules.

c) They no longer carry receptors for signal molecules.

d) They no longer have active nuclei.

a

The cell cycle is regulated at the molecular level by a set of proteins known as

a) cohesins.

b) ATPases.

c) cyclins.

d) separase proteins.

c

Which of the following characteristics is associated with cancer cells?

a) They stop dividing in culture when growth factors are depleted.

b) They evade the normal controls that trigger programmed cell death.

c) They must be attached to a substrate to divide in culture.

d) They exhibit density-dependent inhibition when growing in culture.

b

Which statement below best explains why cells from advanced malignant tumors are often found to contain damaged chromosomes as well as abnormal numbers of

chromosomes?

a) Tumor cells grow and divide more rapidly than normal cells, which results in chromosome abnormalities.

b) Tumor cells with abnormal chromosomes are no longer regulated by contact inhibition.

c) Tumor cells may complete S phase more than once per cell cycle.

d) Tumor cells are no longer regulated by the checkpoints that normally prevent completion of the cell cycle by cells with chromosome abnormalities.

d

Researchers studying a new cultured cell line observed that the cells did not exhibit either density-dependent inhibition or anchorage dependence. What could they conclude right

away?

a) The cells were originally derived from an elderly organism.

b) The cells have altered series of cell cycle phases.

c) The cells originated in the nervous system.

d) The cells show characteristics of tumors.

d

For a chemotherapeutic drug to be useful for treating cancer cells, which of the following characteristics is most

desirable?

a) It is safe enough to limit all apoptosis.

b) It targets only rapidly dividing cells.

c) It only attacks cells that are density dependent.

d) It does not affect metabolically active cells.

b

Tumor cells grown in tissue culture are most likely to display which of the following characteristics?

a) density-dependent inhibition

b) anchorage dependence

c) a lack of programmed cell death

d) a finite number of cell divisions

c

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

a) M

b) cytokinesis

c) G2

d) G1

e) S

d

How do cancer cells differ from normal cells?

a) Cultured cancer cells exhibit anchorage dependence.

b) Cancer cells may be immortal.

c) Cancer cells trigger chromosomal changes in surrounding cells.

b