Campbell Biology: Ninth Edition - Chapter 12: The Cell Cycle

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Chapter 12 Cell Division / Mitosis Vocabulary: gene, cell division, chromosomes, somatic cells, gametes, chromatin, sister chromatids, centromere, mitosis, cytokinesis, meiosis, mitotic phase, interphase, centrosome, aster, kinetochore, cleavage furrow, cell plate, mitotic spindle, binary fission, transformation, benign tumor, malignant tumor, metastasis Objectives: After attending lectures and studying the chapter, the student should be able to: 1. Define gene as it relates to the genetic mater…

Cell Cycle

An ordered sequence of events in the life of a cell

Mitosis

A process of nuclear division in eukaryotic cells conventionally divided into five stages: prophase, prometaphase, metaphase, anaphase, and telophase. Mitosis conserves chromosome number by allocating replicated chromosomes equally to each of the daughter nuclei.

What are the five stages of mitosis?

PPMAT
Prophase
Prometaphase
Metaphase
Anaphase
Telophase

Prophase

The first stage of mitosis, in which the chromatin condenses into discrete chromosomes visible with a light microscope, the mitotic spindle begins to form, and the nucleolus disappears but the nucleus remains intact.

Prometaphase

The second stage of mitosis, in which the nuclear envelope fragments and the spindle microtubules attach to the kinetochores of the chromosomes.

Metaphase

The third stage of mitosis, in which the spindle is complete and the chromosomes, attached to microtubules at their kinetochores, are all aligned at the metaphase plate.

Anaphase

The fourth stage of mitosis, in which the chromatids of each chromosome have separated and the daughter chromosomes are moving to the poles of the cell.

Telophase

The fifth and final stage of mitosis, in which daughter nuclei are forming and cytokinesis has typically begun.

Cytokinesis

The division of the cytoplasm to form two separate daughter cells immediately after mitosis, meiosis I, or meiosis II.

Concept 12.1 Most Cell Division results in genetically identical daughter cells

...

Cell Division

The reproduction of cells

Genome

The genetic material of an organism or virus; the complete complement of an organism's or virus's genes along with its noncoding nucleic acid sequence

Chromosomes

A cellular structure carrying genetic material, found in the nucleus of eukaryotic cells. Each chromosome consists of one very long DNA molecule and associated proteins

Chromatin

The complex of DNA and proteins that makes up eukaryotic chromosomes. When the cell is not dividing, chromatin exists in its dispersed form, as a mass of very long, thin fibers that are not visible with a light microscope

Somatic Cells

Any cell in a multicellular organism except a sperm or egg or their precursors.

Gametes

A haploid reproductive cell, such as an egg or sperm. Gametes unite during sexual reproduction to produce a diploid zygote.

Sister Chromatids

Two copies of a duplicated chromosome attached to each other by proteis at the centromere and sometimes, along the arms. While joined, two sister chromatids make up one chromosome. Chromatids are eventually separated during mitosis or meiosis II

Centromere

In a duplicated chromosome, the region on each sister chromatid where they are most closely attached to each other by proteins that bind to specific DNA sequences; this close attachment causes a constriction in the condensed chromosome. (An uncondensed, unduplicated chromosome has a single centromere, identified by its DNA sequence.)

How many chromatids are in a duplicated chromosome?

2

12.2 The mitotic phase alternates with interphase in the cell cycle

...

mitotic (M) phase

The phase of the cell cycle that includes mitosis and cytokinesis.

interphase

The period in the cell cycle when the cell is not dividing. During interphase, cellular metabolic activity is high, chromosomes and organelles are duplicated, and cell size may increase. Interphase often accounts for about 90% of the cell cycle.

mitotic spindle

An assemblage of microtubules and associated proteins that is involved in the movement of chromosomes during mitosis.

Transformation

(1) The conversion of a normal animal cell to a cancerous cell. (2) A change in genotype and phenotype due to the assimilation of external DNA by a cell. When the external DNA is from a member of a different species, transformation results in horizontal gene transfer

anchorage dependence

The requirement that a cell must be attached to a substratum in order to initiate cell division.

aster

A radial array of short microtubules that extends from each centrosome toward the plasma membrane in an animal cell undergoing mitosis.

benign tumor

A mass of abnormal cells with specific genetic and cellular changes such that the cells are not capable of surviving at a new site and generally remain at the site of the tumor's origin.

binary fission

A method of asexual reproduction by "division in half." In prokaryotes, binary fission does not involve mitosis, but in single-celled eukaryotes that undergo binary fission, mitosis is part of the process.

cleavage

(1) The process of cytokinesis in animal cells, characterized by pinching of the plasma membrane. (2) The succession of rapid cell divisions without significant growth during early embryonic development that converts the zygote to a ball of cells.

density-dependent inhibition

The phenomenon observed in normal animal cells that causes them to stop dividing when they come into contact with one another.

growth factor

(1) A protein that must be present in the extracellular environment (culture medium or animal body) for the growth and normal development of certain types of cells. (2) A local regulator that acts on nearby cells to stimulate cell proliferation and differentiation.

kinetochore

A structure of proteins attached to the centromere that links each sister chromatid to the mitotic spindle.

malignant tumor

A cancerous tumor containing cells that have significant genetic and cellular changes and are capable of invading and surviving in new sites. Malignant tumors can impair the functions of one or more organs.

Metaphase plate

An imaginary structure located at a plane midway between the two poles of a cell in metaphase on which the centromeres of all the duplicated chromosomes are located.

Metastasis

The spread of cancer cells to locations distant from their original site.

MPF

Maturation-promoting factor (or M-phase-promoting factor); a protein complex required for a cell to progress from late interphase to mitosis. The active form consists of cyclin and a protein kinase.

origin of replication

Site where the replication of a DNA molecule begins, consisting of a specific sequence of nucleotides.

somatic cell

Any cell in a multicellular organism except a sperm or egg or their precursors.

transformation

(1) The conversion of a normal animal cell to a cancerous cell. (2) A change in genotype and phenotype due to the assimilation of external DNA by a cell. When the external DNA is from a member of a different species, transformation results in horizontal gene transfer.

Word Roots: ana-

up, throughout, again (anaphase: the mitotic stage in which the chromatids of each chromosome have separated and the daughter chromosomes are moving to the poles of the cell)

Word Roots: bi-

two (binary fission: a type of cell division in which a cell divides in half)

Word Roots: centro-

= the center;

Word Roots: chroma-

= colored (chromatin: DNA and the various associated proteins that form eukaryotic chromosomes)

Word Roots: cyclo-

a circle (cyclin: a regulatory protein whose concentration fluctuates cyclically)

Word Roots: cyto-

= cell;

Word Roots: -kinet

= move (cytokinesis: division of the cytoplasm)

Word Roots: gamet-

= a wife or husband (gamete: a haploid egg or sperm cell)

Word Roots: gen-

= produce (genome: a cell's endowment of DNA)

Word Roots: inter-

= between (interphase: time when a cell metabolizes and performs its various functions)

Word Roots: mal-

= bad or evil (malignant tumor: a cancerous tumor that is invasive enough to impair functions of one or more organs)

Word Roots: meio-

= less (meiosis: a variation of cell division that yields daughter cells with half as many chromosomes as the parent cell)

Word Roots: meta-

between (metaphase: the mitotic stage in which the chromosomes are aligned in the middle of the cell, at the metaphase plate)

Word Roots: mito-

a thread (mitosis: the division of the nucleus)

Word Roots: pro-

before (prophase: the first mitotic stage in which the chromatin is condensing)

Word Roots: soma-

body (centrosome: a nonmembranous organelle that functions throughout the cell cycle to organize the cell's microtubules)

Word Roots: telos-

= an end (telophase: the final stage of mitosis in which daughter nuclei are forming and cytokinesis has typically begun)

Word Roots: trans-

= across; -form shape (transformation: the process that converts a normal cell into a cancer cell)

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.
a plant cell in metaphase.
an animal cell in the S phase of the cell cycle.
a bacterial cell dividing.
an animal cell in the process of cytokinesis.

a plant cell in the process of cytokinesis.

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

inhibition of DNA synthesis.
suppression of cyclin production.
inhibition of regulatory protein phosphorylation.
myosin denaturation and inhibition of cleavage furrow formation.
disruption of mitotic spindle formation.

disruption of mitotic spindle formation.

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

cannot function properly because they are affected by density-dependent inhibition.
are arrested at the S phase of the cell cycle.
are unable to synthesize DNA.
continue to divide even when they are tightly packed together.
are always in the M phase of the cell cycle.

continue to divide even when they are tightly packed together.

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

decreased synthesis of Cdk.
the accumulation of cyclin.
the destruction of the protein kinase Cdk.
the degradation of cyclin.
synthesis of DNA.

the degradation of cyclin.

In the cells of some organisms, mitosis occurs without cytoki-nesis. This will result in

cells with more than one nucleus.
cells lacking nuclei.
cells that are unusually small.
destruction of chromosomes.
cell cycles lacking an S phase.

cells with more than one nucleus.

Which of the following does not occur during mitosis?

condensation of the chromosomes
spindle formation
separation of the spindle poles
separation of sister chromatids
replication of the DNA

replication of the DNA

A particular cell has half as much DNA as some other cells in a mitotically active tissue. The cell in question is most likely in

prophase.
metaphase.
G1.
anaphase.
G2.

G1.

The drug cytochalasin B blocks the function of actin. Which of the following aspects of the animal cell cycle would be most disrupted by cytochalasin B?

cell elongation during anaphase
spindle formation
spindle attachment to kinetochores
cleavage furrow formation and cytokinesis
DNA synthesis

cleavage furrow formation and cytokinesis

asexual reproduction

A type of reproduction involving only one parent that produces genetically identical offspring by budding or by the division of a single cell or the entire organism into two or more parts.

How does Mitosis work?

Mitosis makes it possible for organisms to reproduce asexually, by producing cells that carry the same genes as the parent cells. Note that all the chromosomes of the parent cell are replicated and passed on to the offspring cells. An offspring is literally a "chip off the old block" since its cells are genetically identical to those of the parent.

What is the advantage of sexual reproduction over asexual reproduction?

Sexual reproduction produces greater genetic variation than asexual reproduction. Each offspring inherits a particular combination of genes from two parents; so many combinations are possible that each offspring is essentially unique, differing from its siblings and both parents.

sexual reproduction

A type of reproduction in which two parents give rise to offspring that have unique combinations of genes inherited from the gametes of the two parents.

diploid cell

A cell containing two sets of chromosomes (2n), one set inherited from each parent.

haploid cell

A cell containing only one set of chromosomes (n).

Meiosis

Meiosis is essential to sex, because it enables each parent to contribute one set of chromosomes-- half the total-- to each diploid offspring.

What happens in Meiosis I?

In meiosis I homologous chromosomes pair up, and each pair separates, producing two haploid cells with their sister chromatids still joined.

What happens in Meiosis II?

Meiosis II is like mitosis; sister chromatids separate and four haploid cells are formed. Note that each has half the chromosomes of the parent cell. These cells differ genetically from each other and from the cells of the parents.

What happens in Interphase?

During the interphase prior to meiosis, chromosomes replicate.

What is Mitosis?

Cell division that generates new cells for growth and repair. The division of one cell into two genetically identical daughter cells

What are the three roles of Mitosis?

Growth
Asexual Reproduction
Replacement

What are the 7 Phases of the Cell Cycle?

Interphase
-S- Phase
-G2 Phase
Mitotic Phase
-Mitosis
-Cytokinesis
G1

What happens in the mitotic phase?

Cell division occurs during this short phase, which generally involves two discrete processes: the contents of the nucleus (mainly the duplicated chromosomes) are evenly distributed to two daughter nuclei, and the cytoplasm divides in two.

What happens in the S Phase?

DNA synthesis (or replication) occurs during this phase. At the beginning of the phase, each chromosome is single. At the end, after DNA replication, each chromosome consists of two sister chromatids.

What happens during Interphase?

Typically, this phase accounts for 90% of the cell cycle. It is a time of high metabolic activity. The cell grows by producing proteins and organelles, and chromosomes are replicated.

What happens during mitosis?

This is when division of the nucleus occurs. The chromosomes that have been replicated are distributed to two daughter nuclei.

What happens during G2?

This third subphase of interphase is a period of metabolic activity and growth. During this phase the cell makes final preparations for division.

What happens during G1?

This is the portion of the cell cycle just after division, but before DNA synthesis. During this time the cell grows by producing proteins and organelles.

What happens during cytokinesis?

This is the step in the cell cycle when the cytoplasm divides in two.

Of what two processes does cell division consist of?

Mitosis and Cytokinesis

Cell division consists of two processes: mitosis and cytokinesis. Mitosis— division of the nucleus and its chromosomes— is divided into five phases: prophase, prometaphase, metaphase, anaphase, and telophase. Mitosis is followed by cytokinesis, when the cytoplasm splits to form two separate daughter cells.

What happens during prophase?

1. The nucleoli disappear
2. Chromatin fibers coil up to become discrete chromosomes. 3. Each chromosome consists of two identical sister chromatids, joined at the centromere.
4. Microtubules grow out from the centrosomes, initiating formation of the mitotic spindle.

What happens during prometaphase?

1. The nuclear envelope breaks into fragments.
2. Some of the spindle fibers reach the chromosomes and attach to kinetochores, structures made of proteins and specific sections of DNA at the centromeres.
3. Nonkinetochore microtubules overlap with those coming from the opposite pole.

What happens during metaphase?

1. The mitotic spindle is fully formed
2. The microtubules attached to kinetochores move the chromosomes to the metaphase plate, an imaginary plane equidistant from the poles.

What happens during anaphase?

1. The two centromeres of each chromosome come apart, separating the sister chromatids.
2. Once separate, each sister chromatid is considered a full-fledged daughter chromosome.
3. Motor proteins of the kinetochores "walk" the daughter chromosomes along the spindle microtubules toward opposite poles
4. Microtubules shorten.
5. At the same time, the spindle microtubules not attached to chromosomes lengthen, pushing the two poles farther apart and elongating the cell.

What happens during Telophase?

1. nuclear envelopes form around the identical sets of chromosomes at the two poles of the cell.
2. The chromosomes uncoil
3. Nucleoli appear in the two new nuclei.
4. Meanwhile, cytokinesis begins, splitting the cytoplasm and separating the two daughter cells.

How is Cytokinesis different in Animal Cells?

In animal cells, cytokinesis begins with the formation of a cleavage furrow. At the site of the furrow, a ring of microfilaments contracts, much like the pulling of drawstrings. The cell is pinched in two, creating two identical daughter cells.

How is cytokinesis different in plant cells?

In plant cells, cytokinesis begins when vesicles containing cell-wall material collect in the middle of the cell. The vesicles fuse, forming a large sac called the cell plate. The cell plate grows outward until its membrane fuses with the plasma membrane, separating the two daughter cells. The cell plate's contents join the parental cell wall. The result is two daughter cells, each bounded by its own continuous plasma membrane and cell wall.

G1 Phase

The first gap, or growth phase, of the cell cycle, consisting of the portion of interphase before DNA synthesis begins.

S Phase

The synthesis phase of the cell cycle; the portion of interphase during which DNA is replicated.

G2 Phase

The second gap, or growth phase, of the cell cycle, consisting of the portion of interphase after DNA synthesis occurs.

Centrosome

A structure present in the cytoplasm of animal cells that functions as a microtubule-organizing center and is important during cell division. A centrosome has two centrioles.

Metaphase Plate

An imaginary structure located at a plane midway between the two poles of a cell in metaphase on which the centromeres of all the duplicated chromosomes are located.

Cleavage Furrow

The first sign of cleavage in an animal cell; a shallow groove around the cell in the cell surface near the old metaphase plate.

Cell Plate

A membrane-bounded, flattened sac located at the midline of a dividing plant cell, inside which the new cell wall forms during cytokinesis.

Binary Fission

A method of asexual reproduction by "division in half." In prokaryotes, binary fission does not involve mitosis, but in single-celled eukaryotes that undergo binary fission, mitosis is part of the process.

Compare cytokinesis in animal cells and in plant cells

...

What is the function of nonkinetichore microtubules?

...

Compare the roles of tubulin and actin during eukaryotic cell division with the roles of tubulin like and actin like proteins during bacterial binary fission

...

12.3 The eukaryotic cell cycle is regulated using a molecular control system

...

Cell cycle control system

A cyclically operating set of molecules in the eukaryotic cell that both triggers and coordinates key events in the cell cycle.

Checkpoint

A control point in the cell cycle where stop and go-ahead signals can regulate the cycle.

G0 Phase

A nondividing state occupied by cells that have left the cell cycle, sometimes reversibly.

Cyclin

A cellular protein that occurs in a cyclically fluctuating concentration and that plays an important role in regulating the cell cycle.

Cyclin-dependent kinases

A protein kinase that is active only when attached to a particular cyclin.

Growth Factor

(1) A protein that must be present in the extracellular environment (culture medium or animal body) for the growth and normal development of certain types of cells. (2) A local regulator that acts on nearby cells to stimulate cell proliferation and differentiation.

Density Dependent Inhibition

The phenomenon observed in normal animal cells that causes them to stop dividing when they come into contact with one another.

Anchorage Dependence

The requirement that a cell must be attached to a substratum in order to initiate cell division.

How does MPF allow a cell to pass the G2 Phase checkpoint and enter mitosis?

...

What phase are most of your body cells in?

Most body cells are in a nondividing state called G0

Compare and contrast a benign tumor with a malignant tumor

...

Differentiate between the terms Chromosome, Chromatin and chromatid

...

In which of the three subphases of interphase and the stages of mitosis do chromosomes exist as a single DNA molecule?

...

Explain the significance of the G1, G2, and M checkpoints and the go-ahead signals involved in the cell cycle control system

...

The person credited with first recognizing (in the 1860s) that living cells cannot arise spontaneously, but arise only from previously existing cells, is _____. ( Overview)
Robert Hooke
Rudolf Virchow
Louis Pasteur
Anton van Leeuwenhoek
Watson

Rudolf Virchow

The function of the mitotic cell cycle is to produce daughter cells that _____. (eText Concept 12.1)

are genetically identical to the parent cell (assuming no mutation has occurred)

The region of a chromosome holding the two double strands of replicated DNA together is called _____. (eText Concept 12.1)

a centromere

The centromere is a region in which _____. (eText Concept 12.1)

sister chromatids are attached to one another in prophase

How many maternal chromosomes are present in a somatic human cell not engaged in cell division? (eText Concept 12.1)

23

Human somatic cells contain a total of 46 chromosomes, half of which are maternally derived.

"Cytokinesis" refers to _____. (eText Concept 12.1)

division of the cytoplasm

Cytokinesis is the division of the cytoplasm that follows the mitotic division of the nucleus.

If a somatic human cell is just about to divide, it has _____ chromatids. (eText Concept 12.2)

92

Correct. Human somatic cells have 92 chromatids just prior to cell division due to the replication of the 46 chromosomes that occurred during the S phase.

In telophase of mitosis, the mitotic spindle breaks down and the chromatin uncoils. This is essentially the opposite of what happens in _____. (eText Concept 12.2)

Prophase

During prophase, we observe the formation of the spindle, the condensation of chromatin, and the disappearance of the nucleolus.

What is the difference between a benign tumor and a malignant tumor? (eText Concept 12.3)

Cells of benign tumors do not metastasize; those of malignant tumors do.

Which of the following is false regarding sister chromatids? ( Concept 12.1)
Both of the sister chromatids end up in the same daughter cell after cytokinesis has occurred.

Sister chromatids are attached to one another at the centromere.

Sister chromatids are separated during mitosis.

Sister chromatids are created when DNA is replicated.

Sister chromatids form in the S-phase stage of the cell cycle.

Both of the sister chromatids end up in the same daughter cell after cytokinesis has occurred.

This statement is false. Each of the sisters ends up in a different cell after cell division.

The complex of DNA and protein that makes up a eukaryotic chromosome is properly called _____. (eText Concept 12.1)

chromatin

A cell entering the cell cycle with 32 chromosomes will produce two daughter cells, each with _____. ( Concept 12.1)

64 chromosomes

32 pairs of chromosomes

64 pairs of chromosomes

16 chromosomes

None of the listed responses is correct.

None of the listed responses is correct.

Chromatids are _____. ( Concept 12.1)

found only in aberrant chromosomes

composed of RNA

identical copies of each other if they are part of the same chromosome

held together by the centrioles

the bacterial equivalent of eukaryotic chromosomes

identical copies of each other if they are part of the same chromosome

If a cell contains 60 chromatids at the start of mitosis, how many chromosomes will be found in each daughter cell at the completion of the cell cycle? ( Concept 12.2)

120

45

60

30

15

30

At the completion of the cell cycle, each daughter cell will have the same chromosomal complement as the parent cell.

A biochemist measured the amount of DNA in cells growing in the laboratory and found that the quantity of DNA in the cells doubled _____. (eText Concept 12.2)

between the G1 and G2 phases

A cell biologist carefully measured the quantity of DNA in grasshopper cells growing in cell culture. Cells examined during the G2 phase of the cell cycle contained 200 units of DNA. What would be the amount of DNA at G1 of the cell cycle in one of the grasshopper daughter cells? (eText Concept 12.2)

100 units

During interphase, the genetic material of a typical eukaryotic cell is _____. (eText Concept 12.2)

dispersed in the nucleus as long strands of chromatin

DNA replication occurs in _____. ( Concept 12.2)

the G1 phase of interphase in reproductive cells only

the cytokinesis portion of the cell's life cycle

prophase of both mitosis and meiosis

the S phase of interphase in both somatic and reproductive cells

metaphase of meiosis only

the S phase of interphase in both somatic and reproductive cells

Down syndrome is characterized by cells having three copies of chromosome 21. As a cell in an individual with Down syndrome prepares to enter mitosis, how many chromatids would be present? ( Concept 12.2)

23

94

46

98

92

94

During what phase in the cell cycle would you find the most DNA per cell? (eText Concept 12.2)

G2

Binary Fission

More than likely mitosis evolved from Binary Fission

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