Ch 14

Question 1

the stages through which a cell passes from one cell division to the next constitute the _______

Answer 1

cell cycle

Question 2

Based on cell activities readily visible in the light microscope, there are two major cell cycle phases, _______ and ______

Answer 2

M phase, interphase

Question 3

The separation of duplicated chromosomes into two daughter nuclei is known as

Answer 3

mitosis

Question 4

The separation of the entire cell and its cytoplasm into two daughter cells is known as

Answer 4

cytokinesis

Question 5

What evidence suggests that a cell spends the majority of its time in interphase?

a) interphase is more useful
b) only a small percentage of cells in a tissue or cell culture are seen to be in mitosis
c) a large percentage of cells in a tissue or cell culture are seen to be in mitosis
d) a moderate percentage of cells in a tissue or cell culture are seen to be in mitosis
e) mitosis is too intricate to last very long

Answer 5

b) only a small percentage of cells in a tissue or cell culture are seen to be in mitosis

Question 6

What is the average length of M phase?

a) about 1 hr
b) about 10 mins
c) about 10 hrs
d) 4hrs & 35mins
e) about a day

Answer 6

a) about 1 hr

Question 7

What is the average length of interphase?

a) exactly 10hrs in all cells
b) 12 hrs long
c) not a good average since it may extend for days, weeks or longer depending on the cell type and the conditions
d) may last up to a day
e) lasts about 3hrs

Answer 7

c)not a good average since it may extend for days, weeks or longer depending on the cell type and the conditions

Question 8

When do most of the preparations for mitosis occur, including such activities as DNA replication?

Answer 8

interphase

Question 9

The period in the cell cycle between the end of cell division and the beginning of DNA synthesis is call the __ phase

Answer 9

G1

Question 10

DNA replication and the production of additional histones occur during what part of the cell cycle?

Answer 10

S phase

Question 11

The total length of the cell cycle of cells in a cell culture is 24 hrs. M phase is found to be 1 hr, S phase is found to be 9hrs, and G2 is 4.5hrs. How long is G1?

Answer 11

9.5 Hrs

Question 12

Which cells typically have very short cell cycles on the order of less than 30 minutes?

a) cells in a cleaving frog embryo
b) mammalian liver tissue
c) mammalian muscle cells
d) both a & c
e) nerve cells

Answer 12

a) cells in a cleaving frog embryo

Question 13

Which cells typically have cell cycles lasting several months?

a) cells in a cleaving frog embryo
b) mammalian liver tissue
c) mammalian embryo cells
d) both a & c
e) nerve cells

Answer 13

b) mammalian liver tissue

Question 14

What stimulus can induce liver cells to proliferate?

a) interaction with an appropriate antigen
b) interaction with an appropriate antibody
c) surgical removal of part of the liver
d) a buildup of bile in the liver
e) glycogen buildup in the liver

Answer 14

c) surgical removal of part of the liver

Question 15

Which of the cells below normally possess a relatively high level of mitotic activity?

a) stem cells of various adult tissues
b) hematopoietic stem cells that give rise to red and while blood cells
c) stem cells at the base of numerous epithelia that line the body cavities
d) the relatively unspecialized cells found near the tips of plant roots and stems
e) All of these are correct.

Answer 15

e) all of these are correct

Question 16

What property below do stem cells not share with most cells?

a) They exhibit asymmetric cell division.
b) They do not replicate their DNA before cell division.
c) The two daughter cells have different properties or fates.
d) They exhibit symmetric cell division.
e) They exhibit asymmetric cell division and the two daughter cells have different properties or fates.

Answer 16

e) They exhibit asymmetric cell division and the two daughter cells have different properties or fates.

Question 17

Asymmetric divisions ______.

1) allow stem cells to engage in self-immolation
2) allow stem cells to engage in apoptosis
3) allow stem cells to engage in self-renewal
4) allow stem cells to engage in the formation of differentiated tissue cells

Answer 17

3 & 4

Question 18

Which part of the cell cycle is the most variable?

a) G1 phase
b) S phase
c) G2 phase
d) M phase
e) G0 phase

Answer 18

a) G1 phase

Question 19

Cells that have stopped dividing and are arrested in a stage preceding the initiation of DNA
synthesis are said to be in a ______ state.

Answer 19

G0 phase

Question 20

What must happen in order for a cell to move to S phase from G1?

Answer 20

It must receive a growth-promoting signal.

Question 21

What disease can be defined as resulting from a breakdown in a cell’s ability to regulate its
own division?

Answer 21

cancer

Question 22

You are carrying out experiments in cell fusion by fusing together cells at different stages of
the cell cycle. You then observe the behavior of each nucleus residing in the combined
cytoplasm of the two cells. Which of the following responses would occur if you fused a G2 cell
to a cell in the M phase?
1) The nucleus from the G1 cell started to replicate its DNA.
2) The G2 nucleus undergoes premature chromosomal condensation to form a set of elongated
compacted chromosomes.
3) The M phase nucleus is affected in such a way that its compacted chromosomes decondense.
4) The G2 nucleus undergoes premature chromosomal condensation, but the compacted
chromosomes are visibly doubled.

Answer 22

4) The G2 nucleus undergoes premature chromosomal condensation, but the compacted
chromosomes are visibly doubled.

Question 23

You are carrying out experiments in cell fusion by fusing together cells at different stages of
the cell cycle. You then observe the behavior of each nucleus residing in the combined

cytoplasm of the two cells. Which of the following responses would occur if you fused an S-
phase cell to a cell in the M phase?

a) The nucleus from the M phase cell started to replicate its DNA.
b) The S-phase nucleus undergoes premature chromosomal condensation to form a set of
elongated compacted chromosomes.
c) The M phase nucleus is affected in such a way that its compacted chromosomes decondense.
d) The chromatin in the S-phase nuclei is compacted, but pulverized chromosomal fragments
form.
e) The S-phase nucleus undergoes premature chromosomal condensation; the compacted
chromosomes are visibly doubled.

Answer 23

d) The chromatin in the S-phase nuclei is compacted, but pulverized chromosomal fragments
form.

Question 24

The regulatory subunit of maturation-promoting factor ________.
a) transfers a phosphate group to certain serine and threonine residues of specific protein
substrates
b) is called cyclin because its concentration rises and falls predictably as the cell cycle progresses
c) converts ATP to ADP
d) converts ADP to ATP
e) transfers a phosphate group to certain tyrosine residues of specific protein substrates

Answer 24

b) is called cyclin because its concentration rises and falls predictably as the cell cycle progresses

Question 25

The first transition point in yeast cells that commits the cells to entering S phase occurs just before the end of ___ and is called _______. a) G2, START b) G1, MPF c) G2, MPF d) G1, BEGIN e) G1, START

Answer 25

e) G1, START

Question 26

``` Mammalian cells pass through a point comparable to START during G1, at which time they become committed to DNA replication and, ultimately, the completion of mitosis. What is this point called? a) START b) the restriction point c) the limitation point d) the commitment point e) BEGIN ```

Answer 26

b) the restriction point

Question 27

What external stimulation is required by mammalian cells to progress through the cell cycle prior to reaching the restriction point? a) presence of steroid hormones in their culture medium b) presence of Na+ ions in their culture medium c) presence of growth factors in their culture medium d) no external stimulation is required

Answer 27

c) presence of growth factors in their culture medium

Question 28

``` What multiprotein complex has recently been shown to play a significant role in chromosome compaction? a) compressin b) condensin c) elastin d) loopin e) mitosin ```

Answer 28

b) condensin

Question 29

What happens if any of the condensin proteins are removed from the frog egg extracts within which chromosome compaction can occur in vitro? a) Compaction continues unabated. b) Compaction occurs more quickly than normal. c) Compaction is prevented. d) The DNA expands further and fills the entire cell. e) Compaction occurs but occurs more slowly.

Answer 29

c) compaction is prevented

Question 30

What activates condensin at the onset of mitosis? a) Na+ ions b) phosphorylation of several of its subunits by the Cdk-cyclin that drives cells from G2 into mitosis c) phosphorylation of several of its subunits by the Cdk-cyclin that drives cells from G1 into mitosis d) phosphorylation of several of its subunits by the Cdk-cyclin that drives cells from G1 into S phase e) dephosphorylation of several of its subunits by the Cdk-cyclin that drives cells from G2 into mitosis

Answer 30

b)phosphorylation of several of its subunits by the Cdk-cyclin that drives cells from G2 into mitosis

Question 31

What is responsible for holding sister chromatids together after replication? It holds the two chromatids together through G2 and into mitosis.

Answer 31

b) cohesin

Question 32

What appears to be responsible for the tighter adhesion between chromosomes seen at centromeres rather than along the chromosome arms? a) elevated phosphorylation b) a kinase found at the centromere that phosphorylates cohesin c) a phosphatase found at the centromere that removes phosphate groups from cohesin if they are added d) a phosphatase found in the chromosome arms that removes phosphate groups from cohesin e) a phosphatase found in the chromosome arms that adds phosphate groups to cohesin

Answer 32

c) a phosphatase found at the centromere that removes phosphate groups from cohesin if they are added

Question 33

At the outer surface of the centromere of each chromatid is a proteinaceous, buttonlike structure called the __________.

Answer 33

kinetochore

Question 34

``` As cells enter mitosis, their microtubules disassemble and then reassemble forming the mitotic spindle with a focus at the ________, a special animal cell microtubule-organizing structure. a) kinetosome b) centrosome c) kinetochore d) centromere e) chromosome ```

Answer 34

b) centrosome

Question 35

``` How would you describe the orientation of the two centrioles of the centrosome relative to each other? a) oriented at right angles b) oriented in the same direction c) obverse d) reversed e) converse ```

Answer 35

a) oriented at right angles

Question 36

``` The sunburst arrangement of microtubules that forms around each centrosome during early prophase is called a(n) ________. a) sunburst b) arnost c) aster d) astral fiber e) barrel ```

Answer 36

c) aster

Question 37

What apparently drives the separation of centrosomes? a) motor proteins associated with microfilaments b) motor proteins associated with adjacent microtubules c) contraction of individual microfilaments d) sliding of adjacent microfilaments over one another e) contraction of adjacent microtubules

Answer 37

b) motor proteins associated with adjacent microtubules

Question 38

What controls the progression of a cell from G2 to M? a) mitotic Cdk b) synthetic Cdk c) the spindle d) chromosome compaction e) mitotic Cpk

Answer 38

a) mitotic Cdk

Question 39

What allows the interaction between the mitotic spindle and the chromosomes to occur? a) nuclear envelope breakdown b) nucleosome breakdown c) nucleolus breakdown d) chromatin dissolution e) chromosome condensation

Answer 39

a) nuclear envelope breakdown

Question 40

As revealed by recent studies, which organelles do not seem to remain intact during mitosis? a) mitochondria b) Golgi complex c) ER d) peroxisomes e) chloroplasts

Answer 40

b) Golgi complex

Question 41

The current view of the fate of the ER during mitosis is that ________. a) the ER network remains relatively intact during mitosis b) the ER is broken into its component macromolecules during mitosis, but it is built up from scratch after mitosis c) the ER is broken up into small vesicles that reassemble later d) the ER becomes part of the Golgi complex during mitosis e) the ER joins with mitochondria at the beginning of mitosis

Answer 41

a) the ER network remains relatively intact during mitosis

Question 42

What is an alternative to the classical view of the fate of the membranous portion of the nuclear envelope? a) fragmentation into a population of small vesicles that disperse throughout the mitotic cell b) absorption of the membranes of the nuclear envelope into the membranes of the Golgi complex c) absorption of the membranes of the nuclear envelope into the membranes of the peroxisomes d) absorption of the membranes of the nuclear envelope into the membranes of the ER e) absorption of the membranes of the nuclear envelope into the membranes of the nucleoplasm

Answer 42

d) absorption of the membranes of the nuclear envelope into the membranes of the ER

Question 43

What is the event that begins prometaphase? a) the complete compaction of the chromosomes b) the disappearance of the nucleolus c) the dissolution of the nuclear envelope d) the reappearance of the nucleolus e) the completion of the connection of chromosomes to the spindle

Answer 43

c) the dissolution of the nuclear envelope

Question 44

``` Which stage of mitosis starts as sister chromatids split apart and begin to move toward opposite poles? a) prophase b) metaphase c) prometaphase d) anaphase e) telophase ```

Answer 44

d) anaphase

Question 45

What is the name of the process during which chromosome number is reduced so that each cell has a haploid number of chromosomes? a) mitosis b) meiosis c) cytokinesis d) sexual differentiation e) meitosis

Answer 45

b) meiosis

Question 46

Cells that have a single set of chromosomes are said to have a _______ number of chromosomes; cells that contain two full sets of paired chromosomes are said to have a ______ number of chromosomes.

Answer 46

haploid, diploid

Question 47

What occurs during pairing of chromosomes in prophase of meiosis I that increases genetic variability? a) further condensation of chromosomes b) genetic recombination between homologous chromosomes c) lots of mutations d) chromosomes lose lots of fragments e) gene duplication

Answer 47

b) genetic recombination between homologous chromosomes

Question 48

As they separate, homologous chromosomes are seen to remain attached to each other at specific points by X-shaped structures at the crossover sites called _________.

Answer 48

chiasmata

Question 49

Crossing-over is important for ___________. 1) for ensuring proper chromosome segregation 2) for ensuring proper chromosome miscegenation 3) introducing additional genetic variation into the population 4) delaying meiosis for an appropriate and necessary amount of time

Answer 49

1 & 3

Question 50

At metaphase I, the two homologous chromosomes of each bivalent are connected to spindle fibers from the _________. a) same spindle pole b) opposite spindle poles c) the centromere of its neighboring chromosome d) the centromere of its homologue e) random centromeres of other chromosomes

Answer 50

b) opposite spindle poles

Question 51

Kinetochores of sister chromatids are connected as a unit to microtubules from __________. a) the same spindle pole b) opposite spindle poles c) the centromere of its neighboring chromosome d) the centromere of its homologue e) random centromeres of other chromosomes

Answer 51

a) the same spindle pole

Question 52

``` The random assortment of chromosomes at anaphase I accounts for a large amount of the _________ within a species. a) stability b) genetic variability c) biochemical inhibition d) genetic uniformity e) genetic forbearance ```

Answer 52

b) genetic variability

Question 53

During which stage of meiosis is cohesion between chromosome arms lost? The homologous chromosomes of each bivalent separate during this stage as well, but the cohesion between the sister chromatids and their centromeres remains strong. a) anaphase II of meiosis b) anaphase I of meiosis c) telophase I of meiosis d) metaphase I of meiosis e) telophase II of meiosis

Answer 53

b) anaphase I of meiosis

Question 54

What is required for the separation of homologous chromosomes at anaphase I? a) the separation of sister centromeres b) the dissolution of the chiasmata c) the dissolution of the centromeres d) the dissolution of the centrosomes e) the separation of nucleosomes

Answer 54

b) the dissolution of the chiasmata

Question 55

During which phase of meiosis do the kinetochores of sister chromatids face opposite poles as they line up in the center of the cells? The centromeres of sister chromatids become attached to chromosomal spindle fibers from opposite spindle poles. a) prophase II b) metaphase II c) anaphase II d) metaphase I e) telophase II

Answer 55

b) metaphase II