8
HOW CELLS -REPRODUCE
Henrietta's Immortal Cells
OVERVIEW OF CELL DIVISION MECHANISMS
Mitosis, Meiosis, and the Prokaryotes
Key Points About Chromosome Structure
INTRODUCING THE CELL CYCLE
The Wonder of Interphase
Mitosis and the Chromosome Number
A CLOSER LOOK AT MITOSIS
DIVISION OF THE CYTOPLASM
Cleavage in Animals
Cell Plate Formation in Plants
Appreciate the Process!
WHEN CONTROL IS LOST
The Cell Cycle Revisited
Checkpoint Failure and Tumors
Characteristics of Cancer
Interactive Exercises
Henrietta's Immortal Cells [pp.124-I25]
8.1. OVERVIEW OF CELL DIVISION MECHANISMS [pp.126-I27]
8.2. INTRODUCING THE CELL CYCLE [pp.128-I29]
(
For additional practice, use the interactive vocabulary exercises linked with your BiologyNow CD-ROM.
Selected Words: HeLa cells [p.125], somatic cells [p.126], germ cells [p.126], histone proteins [p.126], GI, S,
and G2 [p.128], 2n [p.129], XY [p.129], prophase, metaphase, anaphase, and telophase [p.129]
Boldfaced Terms
[p.126] mitosis _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
[p.126] meiosis
[p.126] chromosome _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
[p.126] sister chromatids _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
[p.127] nucleosome _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
How Cells Reproduce 93
[p.127] centromere _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
[p.128] cell cycle _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
[p.128] interphase _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
[p.129] chromosome number _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
[p.129] diploid number _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
[p.129] bipolar mitotic spindle _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
Short Answer
1. Describe the origin and the significance of HeLa cells. [pp.124-125]
Matching
Match each term with its description.
2. _._._ centromere [p.127]
3. _ _ chromosome [p.126]
4. _ _ somatic cells [p.126]
5. _ _ sister chromatids [p.126]
6. ___ mitosis and meiosis [p.126]
7. _ _ nucleosome [p.126]
8. _ _ gametes [p.126]
9. _ _ mitosis [p.126]
10. _ _ meiosis [p.126]
11. _ _ histones [p.126]
12. _ _ prokaryotic fission [p.126]
94 Chapter Eight
a. Sex cells, such as sperm and eggs, that function in sexual
reproduction
b. Composed of a chromosome and its copy attached to
each other until late in the division process
c. Cell divisions that give rise to gametes or spores;
functions in sexual reproduction
d. An organizational unit composed of a histone-DNA
spool
e. Chromosomal proteins; appear rather like beads on a
string
f. In bacterial cells only, the basis of asexual reproduction
g. Body cells
h. A pronounced constricted region on a chromosome;
docking site for certain microtubules that take part in
nuclear division
i. Cell divisions by which an organism grows, replaces
worn-out cells, and repairs tissues; used by single-celled
organisms for asexual reproduction
j. Composed of a molecule of DNA and its proteins
k. The nuclear division mechanisms
Identification
Identify the stage in the cell cycle indicated by each number in the diagram. [p.128]
13.
---------21
14. _ _ __
IS. _ _ __
16. _ _ __
13
14
17. _ _ __
18. _ _ __
~
r§'~
19. _ _ __
",0 0°
:s;.'1i ~
20. _ _ __
&.
;..0
09 Q,'1i
21. _ _ __
i§' .~
15
22. _ _ __
23. _ _ __
Matching
Link each time span identified below with the most appropriate number in the preceding diagram. [p.128]
24. ___ Interval following DNA replication; cell prepares to divide
25. ___ The complete period of nuclear division, followed by cytoplasmic division (a separate event)
26. ___ Interval of cell growth, when DNA replication is completed (chromosomes duplicated)
27. ___ Interval of cell growth, before DNA duplication (chromosomes unduplicated)
28. ___ Usually the longest part of a cell cycle
29. ___ Interval of cytoplasmic division
30. _ _ Period that includes G1, S, and G2
8.3. A CLOSER LOOK AT MITOSIS [pp.130-131]
8.4. DIVISION OF THE CYTOPLASM [pp.132-133]
Selected Words: threadlike form [p.130], thick, compact, rod-shaped forms [p.130], two barrel-shaped
centrioles [p.130l, aligned midway between the poles [p.130]
Boldfaced Terms
[p.130] prophase _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
[p.130] centrosome _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
[p.130] metaphase
How Cells Reproduce 95
[p.130] anaphase _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
[p.131] telophase _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
[p.132] cleavage
[p.133] cell plate formation _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
Identification
Identify each mitotic stage shown. Select from late prophase, transition to metaphase (prometaphase), cell at
interphase, metaphase, early prophase, telophase, interphase-daughter cells, and anaphase. Complete the exercise
by entering the letter of the correct phase in the parentheses.
-----{ )
[p.131]
2_____ { )
[p.131]
3_____ { )
[p.130]
4_____{ )
[p.131]
5_____{ )
[p.130]
6_ _ _ _ _ { )
[p.130]
7_____ { )
8 _____ { )
[p.131]
[p.130]
a. Attachments between two sister chromatids of each chromosome break; the two are now separate
chromosomes, which microtubules move to opposite spindle poles.
b. Microtubules penetrate the nuclear region and collectively form the bipolar spindle apparatus;
microtubules become attached to the two sister chromatids of each chromosome.
c. The DNA and its associated proteins have started to condense.
d. All the chromosomes are now fully condensed and lined up at the equator of the fully formed
microtubule spindle; chromosomes are now in their most tightly condensed form.
e. The cell duplicates its DNA and prepares for nuclear division.
f. Two daughter cells have formed; each is diploid with two of each type of chromosome, just like the
parent cell's nucleus.
g. Chromosomes continue to condense; new microtubules become assembled; they move one of two
centriole pairs toward the opposite end of the cell; the nuclear envelope begins to break up.
h. There are two clusters of chromosomes, which decondense; patches of new membrane fuse to form a
new nuclear envelope; mitosis is complete.
96 Chapter Eight
Choice
Choose from the following:
a. plant cells
b. animal cells
9. Formation of a cell plate [p.133]
_ _ _ _ 10. As the microfilament ring shrinks in diameter, it pulls the cell surface inward [p.132]
_ _ _ _ 11. Cellulose is deposited inside the sandwich; in time, these deposits will form two cell walls
[p.132]
_ _ _ _ 12. The primary wall of the growing cell is still thin; new material is deposited on it [p.132]
_ _ _ _ 13. A cleavage furrow [p.132]
_ _ _ _ 14. Cellulose deposits form a cementing middle lamella [p.132]
_ _ _ _ 15. A ring of microfilaments attached to the plasma membrane contracts [p.132]
_ _ _ _ 16. Contractions continue; the cell is pinched in two [p.132]
_ _ _ _ 17. As mitosis ends, vesicles cluster at the spindle equator [p.132]
_ _ _ _ 18. Cellulose deposits build up at the plate; in time, they are thick enough to form a cross-wall
through the cell [p.133]
8.5. WHEN CONTROL IS LOST [pp.134-135]
Selected Words: growth factors [p.134], kinases [p.134], inhibit mitosis [p.134], stimulate mitosis [p.134],
oncogene products [p.134], benign [p.135], malignant neoplasm [p.135], metastasis [p.135]
.
Boldfaced Terms
[p.134] neoplasms _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
[p.13S] cancers _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
Short Answer
1. List the four characteristics displayed by all cancer cells. [p.135]
How Cells Reproduce 97
Self-Quiz
Are you ready for the exam? Test yourself on key concepts by taking the additional tests linked with your
BiologyNow CD-ROM.
__ 1. The replication of DNA occurs
_ _ _ _ _ . [p.128]
a. between the growth phases of
interphase
b. immediately before prophase of mitosis
c. during prophase of mitosis
d. during anaphase of mitosis
e. in daughter cells during telophase
__ 2. Each histone-DNA spool is a single
structural unit called a _ _ _ _ __
[p.126]
a. kinetochore
b. motor protein
c. centromere
d. nucleosome
e. gene
__ 3. In the cell life cycle of a particular cell,
_ _ _ _ _ . [p.128]
. a. mitosis occurs immediately after Gl
b. G2 precedes S
c. Gl precedes S
d. mitosis and S precede Gl
e. S occurs immediately before mitosis
__ 4. The correct order of the stages of mitosis is
_ _ _ _ _ . [pp.130-131]
a. prophase, metaphase, telophase,
anaphase
b. telophase, anaphase, metaphase,
prophase
c. telophase, prophase, metaphase,
anaphase
d. anaphase, prophase, telophase,
metaphase
e. prophase, metaphase, anaphase,
telophase
__ 5. During
, sister chromatids
of each chromosome are separated from
each other, and those former partners,
now chromosomes, are moved toward
opposite spindle poles. [pp.130-131]
a. prophase
b. metaphase
c. anaphase
d. telophase
e. transition to metaphase
98 Chapter Eight
__ 6. In the process of cytokinesis, cleavage
furrows are associated with _ _ _ _ __
cell division, and cell plate formation is
associated with
cell
division. [pp.132-133]
a. animal; animal
b. plant; animal
c. plant; plant
d. animal; plant
__ 7. In eukaryotic cells, which of the following
can occur during mitosis? [p.130]
a. Two mitotic divisions to maintain the
parental chromosome number
b. The replication of DNA
c. A long growth period
d. The disappearance of the nuclear
envelope and nucleolus
e. A G2 event
__ 8. The term diploid refers to _ _ _ _ __
[p.129]
a. having two chromosomes of each type
in somatic cells
b. twice the parental chromosome number
c. half the parental chromosome number
d. having one chromosome of each type in
somatic cells
e. the chromosome conditions in a sex cell
__ 9. Somatic cells are _ _ _ _ _ _ cells;
germ cells are
cells. [p.126]
a. meiotic; body
b. body; body
c. meiotic; meiotic
d. body; meiotic
_
10. If a parent cell has sixteen chromosomes
and undergoes mitosis, the resulting cells
will have
chromosomes.
[p.131]
a. sixty-four
b. thirty-two
c. sixteen
d. eight
e. four
_
11. "Microtubules penetrate the nuclear
region. Collectively, they form a bipolar
spindle apparatus." These sentences
describe the
of mitosis.
[p.130]
a. prophase
b. metaphase
c. prometaphase
d. anaphase
e. telophase
Chapter Obj ectives/Review Questions
1. Define the term HeLa cells; explain their origin. [pp.124-125]
2. The terms mitosis and meiosis refer to the division of the cell's
. [p.126]
3. Define the terms somatic cells, gametes, prokaryotic fission, chromosome, nucleosome, sister chromatids, and
centromere. [pp .126-127]
4. List and describe, in order, the various activities that occur in the eukaryotic cell life cycle. [p.128]
5. Interphase of the cell cycle consists of G1,
, and G2. [p.128]
6. S is the time in the cell cycle when
replication occurs. [p.128]
7. Each species has a characteristic
number, the sum of all chromosomes in cells of a
given type. [p.129]
8. The
number of chromosomes in your body cells is 46. [p.129]
9. Describe, in detail, the cellular events occurring in the prophase, metaphase, anaphase, and telophase
of mitosis. [pp.130-131]
10. Describe the number and movements of centrioles in the cell division of some cells. [pp.130"':'131]
11. Compare and contrast cytokinesis as it occurs in plant and animal cell division; use the following
concepts: cleavage furrow, microfilaments at the cell's midsection, and cell plate formation. [pp.132-133]
12. Be able to define the terms growth factors, kinases, oncogenes, neoplasms, benign, malignant neoplasm, basal
cell carcinoma, squamous cell carcinoma, malignant melanoma, metastasis. [pp.134-135]
13. List the four characteristics displayed by all cancer cells. [p.135]
Media Menu Review Questions
Questions 1 and 2 are drawn from the following Infotrac College Edition article: "Cell Cycle Circuits
Mapped." Anonymous. Applied Genetics News, October 2001.
1. The technique discussed in the article is basically one that deals with _ _ _ _ __
a. identifying genes
b. segregation of genes
c. connecting the control switches that make up
the network for any living process
d. mistakes in DNA
2. The cell cycle in yeast is controlled by _ _ _ _ __
a. transcriptional activators
b. antibodies
c. mutations
d. gene therapy
Questions 3-5 are drawn from the following Infotrac College Edition article: "Familiar Proteins Play
Unfamiliar Role in Cell Division." Anonymous. Stem Cell Week, January 21, 2002.
3. The protein, CAF-I, _ _ _ _ _ _ ,
a. can silence regions of chromosomes when acting alone
b. puts together nucleosomes
c. tears apart nucleosomes
d. has no useful function
4. Kaufman and his coworkers had previously demonstrated that CAF-I and another set of proteins,
called Hir, are important for _ _ _ _ __
a. spindle formation
b. alcohol production in yeast
c. "silenced" regions of chromosomes
d. removing proteins from chromosomes
How Cells Reproduce 99
5. When the researchers removed the genes that code for both CAF-1 and Hir proteins, the
a. the growth rate of the yeast slowed markedly
b. yeast lacking these genes lost chromosomes or
gained extra ones hundreds of times more often than ordinary wild yeast
c. histones disappeared
d. spindles disintegrated
e. both a and b are correct
Questions 6 and 7 are drawn from the following Infotrac College Edition article: "HIV Protein Stops Cell
, Division." Anonymous. Virus Weekly, April 9, 2002.
6. HIV protein Vpr stops infected cells from dividing, but in doing so, Vpr _ _ _ _ __
a. strengthens the cell's resources against infection
b. causes cells to enter the G2 phase
c. helps HIV to harness the infected cell's resources to create more HlV
d. increases antibody
production
7. Vpr also _ _ _ _ __
a. stops division of laboratory cultured cells
b. is a major player in G2 cell cycle arrest
c. allows HIV to reproduce very efficiently in the human body
d. a, b, and c are correct
Questions 8-10 are drawn from the following Infotrac College Edition article: "How You Can Lower Your
Cancer Risk." Anonymous. Harvard Health Letter, August 2002.
8. To lower chances of getting cancer, _ _ _ _ _ _ is at the top of everybody's list.
a. careful eating
b. eating lowfat and nonfat
c. staying trim
d. not smoking
e. exercise
9. Consuming the recommended five servings of a variety of fruits and vegetables every day is apparently not associated with lower risk for cancer of the _ _ _ _ __
a. lung and stomach
b. mouth and pharynx
c. breast and prostate cancer
d. esophagus
10. The association of meat consumption with colon and prostate cancer may be due to _ _ _ _ __
a.heterocyclic amines
b. marinates used
c. stearic acid
d. lean cuts
e. both a and c
Integrating and Applying Key Concepts
1. Runaway cell division is characteristic of cancer. Imagine the various points of the mitotic process that
might be sabotaged in cancerous cells in order to halt their multiplication. Then try to imagine how one
might discriminate between cancerous and normal cells to guide those methods of sabotage that are
most effective in combating cancer.
100
Chapter Eight