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Cell Division | Principles of Biology from Nature Education
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Cell Division
Cells have processes for copying and distributing genetic material to daughter cells
during division.
A time­lapse series of images shows cell division in a young embryo.
Successive cell divisions of a fertilized egg create a four­cell embryo at the end of this series. In the top row, a
fertilized egg divides into two cells and then into four cells. The bottom row shows the same seven micrographs
with the cells outlined in red to show how the four cells of the embryo arose from a single fertilized egg.
© 2010 Nature Publishing Group Wong, C.C., et al. Non­invasive imaging of human embryos before embryonic
genome activation predicts development to the blastocyst stage. Nature Biotechnology 28, 1115–1121 (2010)
doi: 10.1038/nbt.1686. Used with permission.
Topics Covered in this Module Overview of Cell Division
Prokaryotic Cell Division
Eukaryotic Cell Division
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Identify the major phases of the eukaryotic cell cycle and describe the major events that occur during each phase.
Explain in detail how mitosis proceeds followed by cytokinesis.
Describe how prokaryotes divide by binary fission.
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32 Cell Division
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Overview of Cell Division
Cells reproduce. That is, one cell divides into two through a process known as cell division. When a parent cell divides,
the two daughter cells are genetically identical (or nearly so) to the parent cell. In multicellular organisms like humans,
cell division enables growth and the replacement of worn­out or damaged cells. For example, the cells lining the
esophagus, the tube that connects the mouth to the stomach, only live for 2 or 3 days before being replaced. Cells may
divide to repair injury, as when skin cells grow over a wound or a broken bone knits. Dividing cells in animal embryos,
known as stem cells, produce all the specialized cells of the body.
Cells divide through one of several methods. Prokaryotes reproduce through binary fission, whereas eukaryotic cells
divide through either mitosis or meiosis. During binary fission, bacteria replicate their genetic material (usually a single
chromosome­like structure) and grow to a certain size before splitting into two daughter cells. Mitosis is the process in
eukaryotes of producing exact copies of the parent cell's chromosomes and segregating them into separate nuclei,
followed by cytokinesis to produce two daughter cells. As in binary fission, the two cells produced by mitosis contain all
the same parts and largely identical genomes. In contrast, meiosis produces daughter cells that contain half the number
of chromosomes of the parent cell; thus, the daughter cells are not exact copies. Meiosis leads to the formation of
gametes, which then fuse with another such gamete during sexual reproduction.
IN THIS MODULE
Overview of Cell Division
Prokaryotic Cell Division
Eukaryotic Cell Division
Summary
Test Your Knowledge
WHY DOES THIS TOPIC MATTER?
Cancer: What's Old Is New Again
Is cancer ancient, or is it largely a
product of modern times? Can
cutting­edge research lead to prevention
and treatment strategies that could make
cancer obsolete?
Synthetic Biology: Making Life from
Bits and Pieces
Scientists are combining biology and
engineering to change the world.
Stem Cells
Stem cells are powerful tools in
biology and medicine. What can
scientists do with these cells and their
incredible potential?
PRIMARY LITERATURE
The memory of iPS cells
Incomplete DNA methylation underlies a
transcriptional memory of somatic cells in
human iPS cells.
View | Download
Genetically­matched iPS cells
more immunogenic than ES cells
Immunogenicity of induced pluripotent stem
cells.
View | Download
Adaptor proteins regulate cell
signaling
Structural basis for regulation of the Crk
signaling protein by a proline switch.
View | Download
The role of cyclin D1 in DNA repair
linked to cancer growth
A function for cyclin D1 in DNA repair
uncovered by protein interactome analyses
in human cancers.
View | Download
SCIENCE ON THE WEB
A View Through a Microscope
Watch a short video of cell division in
different types of cells.
A Population of Mitotic Cells
http://www.nature.com/principles/ebooks/principles­of­biology­104015/29155678/1
1/2
1/20/2015
Cell Division | Principles of Biology from Nature Education
Watch cells dividing in a developing
embryo, and follow the fluorescently­
labeled spindles
Bacteria Dividing
See how bacterial division creates a
colony, starting from a few cells
Dividing Cancer Cells
How long does it take for cancer cells to
grow? Choose your time window and watch
what happens.
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Prokaryotic Cell Division
Prokaryotes divide by binary fission. The prokaryotic cell copies its genome, increases in size and then splits into two
daughter cells. Most bacteria possess just one circular chromosome; there is no nucleus. Although a bacterial genome
is much simpler than a eukaryotic genome, it still holds an enormous amount of information that must be copied
accurately for the daughter cells to survive. Escherichia coli are bacteria that live in the human gut and many other
environments. If stretched out, an E. coli chromosome extends 1,500 times the length of an E. coli cell. Proteins
involved in supercoiling DNA accomplish the feat of packaging the E. coli chromosome into a compact structure.
To watch replication in action, researchers have used fluorescent molecules that label the origin of replication green,
which is the point at which replication of an E. coli chromosome begins. This green region can be viewed through a
fluorescent microscope. As the DNA replicates, the labeled region proceeds in opposite directions from a single point of
origin until the two replication forks meet and complete duplication of the chromosome. The cell elongates and
increases in size. The two copies of the bacterial genome separate and move to opposite ends of the replicating cell or,
in some bacteria, different specific places in the cell. Scientists do not fully understand how the chromosomes move or
how they are anchored to their new locations. They have identified one protein that appears to help the chromosomes
move. Another protein seems to help pinch the plasma membrane together to separate the parent cell into two daughter
cells. Other cellular components gather near the point of division to redirect cell wall formation and prevent DNA
damage. If the DNA replication finishes without errors, each daughter cell will have the same genome as the parent cell.
Do bacteria always reproduce in the same way? Under certain environmental conditions, such as scarce food or danger
of drying out, bacteria switch from reproducing by binary fission to using mechanisms that help ensure their survival
under these more stressful conditions. In harsh environments, many bacteria produce endospores: dormant forms that
can survive under adverse environmental conditions. When nutrients are scarce or the environment becomes
particularly harsh, a common soil bacterium called Bacillus subtilis may produce a resilient endospore within the
parent vegetative cell that can live for thousands of years. When conditions favor the growth of the species, the
endospore germinates, producing a normal bacterium. Other bacteria produce spores as a normal part of their life cycle.
Metabacterium polyspora, a bacterium that lives symbiotically in the guinea pig gastrointestinal tract, produces
endospores. These endospores pass into an individual's feces, which is then eaten by the animal to extract more
nutrients, after which the endospores pass through the stomach and germinate into viable bacteria when they reach the
small intestine.
Three­dimensional microscopy techniques (such as scanning electron microscopy or SEM) can produce images of a
cell's surface, which help scientists visualize bacterial reproduction. Certain bacteria reproduce asymmetrically by
budding, breaking off daughter cells from the tip of the bacterium or the end of a stalk. In some species, the daughter cell
develops immediately into a cell identical to the parent. Other daughter cells enter into a different part of the life cycle.
For instance, Pedomicrobium cells are immobile, but they produce flagellated buds that swim away from the parent
before maturing into immobile adults. The daughter cells move in search of food and improve their survival by reducing
the competition among the newly formed cells.
Test Yourself
What benefits might mobility provide to Pedomicrobium daughter cells?
Submit
Can one division create more than two cells? When environmental conditions are stressful, some bacteria undergo
multiple fission events; some cyanobacteria always reproduce through multiple fission events. The cyanobacteria
Stanieria replicate their DNA but do not notably increase the size of their cytoplasm before cell division. They divide
rapidly many times to produce up to 1,000 small cells called baeocytes. The rupture of the multiple cell walls that have
formed releases the baeocytes. Streptomyces coelicolor grow underground by extending filaments that break into
multiple long cells. When nutrients are depleted, these bacteria extend above ground and release spores into the air.
IN THIS MODULE
Overview of Cell Division
Prokaryotic Cell Division
Eukaryotic Cell Division
Summary
Test Your Knowledge
WHY DOES THIS TOPIC MATTER?
Cancer: What's Old Is New Again
Is cancer ancient, or is it largely a
product of modern times? Can
cutting­edge research lead to prevention
and treatment strategies that could make
cancer obsolete?
http://www.nature.com/principles/ebooks/principles­of­biology­104015/29155678/2
1/2
1/20/2015
Cell Division | Principles of Biology from Nature Education
Synthetic Biology: Making Life from
Bits and Pieces
Scientists are combining biology and
engineering to change the world.
Stem Cells
Stem cells are powerful tools in
biology and medicine. What can
scientists do with these cells and their
incredible potential?
PRIMARY LITERATURE
The memory of iPS cells
Incomplete DNA methylation underlies a
transcriptional memory of somatic cells in
human iPS cells.
View | Download
Genetically­matched iPS cells
more immunogenic than ES cells
Immunogenicity of induced pluripotent stem
cells.
View | Download
Adaptor proteins regulate cell
signaling
Structural basis for regulation of the Crk
signaling protein by a proline switch.
View | Download
The role of cyclin D1 in DNA repair
linked to cancer growth
A function for cyclin D1 in DNA repair
uncovered by protein interactome analyses
in human cancers.
View | Download
SCIENCE ON THE WEB
A View Through a Microscope
Watch a short video of cell division in
different types of cells.
A Population of Mitotic Cells
Watch cells dividing in a developing
embryo, and follow the fluorescently­
labeled spindles
Bacteria Dividing
See how bacterial division creates a
colony, starting from a few cells
Dividing Cancer Cells
How long does it take for cancer cells to
grow? Choose your time window and watch
what happens.
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32 Cell Division
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Eukaryotic Cell Division
Like binary fission, eukaryotic cell division results in two daughter cells that are nearly identical to the parent cell.
Importantly, with mitosis, each daughter cell contains the same number of chromosomes as the parent cell. Most
eukaryotes have several chromosomes. Humans have 23 pairs, or 46 chromosomes. These chromosomes contain 3
billion nucleotide pairs that would extend 2 m (6.5 feet) if stretched out; more than 250,000 times the length of a single
cell. Before cell division, the loosely packed DNA is copied and then condensed into tightly packed chromosomes
(Figure 1). Eukaryotic cell division is a complex process. Unlike prokaryotes, a eukaryotic cell contains membrane­
bound organelles including the nucleus, which must either be divided among or reconstructed within the daughter cells.
Figure 1: Condensed human chromosomes.
Scanning electron micrograph of several human chromosomes in a condensed form prior to cell division.
magnification = 25,000x
Biophoto Associates/Science Source.
In 1882, the German anatomist Walther Flemming (Figure 2a) first recorded the process of mitosis. Flemming was able
to visualize the chromosomes in a single cell using dyes that bound strongly to chromatin, a technique still used by
scientists today (Figure 2b).
Figure 2: Walther Flemming and his late 19th century illustrations of mitosis.
Panel a) Walther Flemming was the first to record the process of mitosis. Panel b) Drawings of mitosis created by
Flemming. These drawings inspired many textbook illustrations.
a) Science Photo Library/Science Source. b) Illustration from Zellsubstanz, Kern und Zelltheilung.
What happens when a cell is not dividing? Using the microscopy techniques of his time, Flemming could determine only
that cells grew larger between divisions. Now we know that mitosis is a small part of the cell cycle, the life cycle of a cell
from the time it first forms until the time it divides (Figure 3). Mitosis (M phase) alternates with interphase — the phase in
which the cell grows and the DNA replicates in preparation for mitosis. Interphase occurs in three subphases: G1 phase
(first gap, in which the cell grows), S phase (synthesis, in which the chromosomes are duplicated), and G2 phase
(second gap, in which the cell grows more and prepares to begin the process of mitosis). Proteins, organelles, and
cytoplasm are produced during the gap phases, but DNA is synthesized only during the S phase. Given the size of most
eukaryotic genomes, copying the genome is a major task of the cell cycle. In a human cell that divides once in 24 hours,
the S phase lasts 6–8 hours, or almost half of the cell cycle. Mitosis takes less than 1 hour. Cells that divide infrequently
spend most of their time either in the G1 phase or in an extended, non­dividing phase called G0 phase.
Figure 3: The cell cycle.
In the cell cycle, interphase includes the G1 , S, and G2 phases. Non­dividing cells can remain in interphase
indefinitely by entering the G0 phase. The relatively short processes of cell division include mitosis and cytokinesis.
© 2012 Nature Education All rights reserved.
Figure Detail
How does the cell prepare for division?
How is the huge amount of DNA in a eukaryotic cell organized? Before and during replication, a cell's DNA is packaged
with histone proteins into densely packed fibers, called chromatin. Replication begins at hundreds or even thousands of
origin points. During replication, specialized proteins (helicases) unwind the DNA double helix and hold it in place while
other enzymes (DNA polymerases) copy the nucleotide sequence. The DNA polymerases constantly proofread the copy
and correct copying errors. Once the copies are complete, the chromatin fibers coil tightly and fold into thick
chromosomes. The two copies of the same chromosome are paired into sister chromatids. Each pair of sister
chromatids are bound together by a DNA­protein complex called the centromere.
A nuclear envelope surrounds the duplicated chromosomes. The cell's centrosome, a structure that organizes
microtubules during mitosis, duplicates during interphase in an animal cell. The two centrosomes stay together near the
nucleus (Figure 4, number 3).
How does the cell divide?
To make sense of the specific events of cell division, scientists have identified five stages of mitosis, although it is
actually a continuous process. These five stages are called prophase, prometaphase, metaphase, anaphase and
telophase (Figure 4, numbers 4­8).
Figure 4: The in­depth cell cycle.
The phases of the cell cycle are delineated by specific events. The M phase (mitosis), where the genetic material is
segregated, is further subdivided into prophase, prometaphase, metaphase, anaphase, and telophase.
© 2013 Nature Education All rights reserved.
Figure Detail
During prophase, in most organisms, the chromatin condenses into chromosomes that are visible with a light
microscope. At this point, the nucleoli and ribosomes disappear, and the mitotic spindle begins to take shape. The
mitotic spindle is a complex structure, consisting of microtubules and associated proteins, that is responsible for
organizing the chromosomes and pulling them apart. Although plant cells lack centrosomes, they do form mitotic
spindles, which are a crucial organizing force in eukaryotic cell division. In prophase, microtubules connected to the
centrosomes grow through the addition of tubulin protein subunits to the ends of the microtubules, lengthening the
microtubules and beginning to push the centrosomes apart.
During prometaphase, as the chromosomes condense further, kinetochore protein complexes attach to the
centromeres that join sister chromatids. The nuclear envelope usually breaks into pieces during prometaphase,
allowing the mitotic spindle to extend across the cell and through the nuclear space. Some of the microtubules bind with
the kinetochores, thus linking together the centrosomes and the chromosomes (Figure 4, number 5) and setting the
stage for the events that occur during metaphase.
During metaphase, specialized motor proteins move the chromosomes along microtubules to the middle of the cell.
The chromosomal centromeres lie on the imaginary plane of the metaphase plate, stretching across the middle of the
cell (Figure 4, number 6). The two kinetochores of each sister chromatid face in opposite directions and are joined by
microtubules to the opposing centrosomes.
During anaphase, proteins attached to the chromatids are released, causing the sister chromatids to rapidly separate.
The newly formed daughter chromosomes move toward opposite ends of the cell, pushed and pulled by motor proteins
along the microtubules (Figure 4, number 7).
In the final stage of mitosis, telophase, fragments of the parent nuclear membrane and other intracellular membranes
join to form a new nuclear envelope around each collection of chromosomes, forming two daughter nuclei. The
chromosomes loosen and straighten out to some extent. The microtubules disintegrate, and mitosis is complete (Figure
4, number 8). The stages of mitosis are recapitulated in a series of photomicrographs (Figure 5).
Mitosis is the process for distributing the cell's duplicated chromosomes equally. How then is the rest of the cell divided
up, ultimately forming two daughter cells? Shortly after mitosis, the cytoplasm finishes dividing through the process of
cytokinesis (Figure 4, number 9 and Figure 5, the two rightmost images). In animal cells, cytokinesis begins with a
cleavage furrow, a narrow groove in the middle of the dividing cell at the location of the former metaphase plate. Actin
microfilaments form a ring around the inside of the cell at the cleavage furrow. The filaments are drawn together,
contracting the ring and pinching the cell membrane together. This pinching action separates the cytoplasm into two
identical daughter cells.
Figure 5: The stages of mitosis and cytokinesis.
A series of photomicrographs show an animal cell undergoing mitosis and cytokinesis. magnification = 500x
Thomas Deerinck, NCMIR/Science Source.
Test Yourself
Mitosis focuses on the nucleus. What other cell structures need to be re­formed or
reorganized in the daughter cells?
Submit
How is cytokinesis different in plants? Plant cells have cell walls. Instead of a cleavage furrow forming, the Golgi
apparatus generates vesicles that move along microtubules to the middle of the cell and join to form a cell plate. Cell
wall materials gather within the cell plate, and the plate enlarges until it joins up with the edges of the plasma
membrane. The plate separates down the middle, producing a new membrane and cell wall for each daughter cell
(Figure 6).
Figure 6: Formation of the cell plate.
In plants, the cell plate forms between two daughter cells, separating them. The cell plate in this transmission
electron micrograph is the bright blue line in the middle of the cell.
David M. Phillips/Science Source.
Test Yourself
Unlike animal cells, the cells of bacteria, plants, fungi and many protists are surrounded by a
cell wall. How might this change the process of cytokinesis?
Submit
Future perspectives.
Errors in cell division and the cell cycle can lead to uncontrolled cell growth, which can result in cancer and other
disorders. Understanding normal cell division may help scientists and doctors find ways to repair or prevent errors in
cell division and the cell cycle. In addition, the human body uses the control of cell division to repair injuries. Knowing
when the body can repair itself helps doctors provide patients with prognoses, and knowing how the repair process
works may allow scientists to encourage or modulate it. For instance, abnormal formation of new neurons in the adult
spinal cord may cause people to feel pain in response to sensations that do not normally cause pain. Transplanting
stem cells to the spinal cord may alleviate these symptoms, perhaps because the stem cells are able to properly control
cell division.
For many years, scientists believed that the neurons in the adult brain did not divide and could not be replaced if they
were lost. During the last 20 years, studies have shown that new neurons can form in the adult brain. For instance,
antidepressant medications can initiate new neurons to form in the hippocampus, a part of the brain associated with
memory. Problems forming new neurons in the hippocampus may increase a person's risk of developing posttraumatic
stress disorder (PTSD), a condition marked by difficulty matching cues to contexts. A returning soldier might hear a loud
noise in the house and respond as if it were a gunshot, although the context of the familiar setting should make a
gunshot unlikely. Stimulating hippocampal neuron development might help this person interpret contexts more
accurately.
IN THIS MODULE
Overview of Cell Division
Prokaryotic Cell Division
Eukaryotic Cell Division
Summary
Test Your Knowledge
WHY DOES THIS TOPIC MATTER?
Cancer: What's Old Is New Again
Is cancer ancient, or is it largely a
product of modern times? Can
cutting­edge research lead to prevention
and treatment strategies that could make
cancer obsolete?
Synthetic Biology: Making Life from
Bits and Pieces
Scientists are combining biology and
engineering to change the world.
Stem Cells
Stem cells are powerful tools in
biology and medicine. What can
scientists do with these cells and their
incredible potential?
PRIMARY LITERATURE
The memory of iPS cells
Incomplete DNA methylation underlies a
transcriptional memory of somatic cells in
human iPS cells.
View | Download
Genetically­matched iPS cells
more immunogenic than ES cells
Immunogenicity of induced pluripotent stem
cells.
View | Download
Adaptor proteins regulate cell
signaling
Structural basis for regulation of the Crk
signaling protein by a proline switch.
View | Download
The role of cyclin D1 in DNA repair
linked to cancer growth
A function for cyclin D1 in DNA repair
uncovered by protein interactome analyses
in human cancers.
View | Download
SCIENCE ON THE WEB
A View Through a Microscope
Watch a short video of cell division in
different types of cells.
A Population of Mitotic Cells
Watch cells dividing in a developing
embryo, and follow the fluorescently­
labeled spindles
Bacteria Dividing
See how bacterial division creates a
colony, starting from a few cells
Dividing Cancer Cells
How long does it take for cancer cells to
grow? Choose your time window and watch
what happens.
page 171 of 989
2 pages left in this module
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Summary of Cell Division | Principles of Biology from Nature Education
Principles of Biology
contents
32 Cell Division
Summary
OBJECTIVE
Identify the major phases of the eukaryotic cell cycle and describe the major events that occur
during each phase.
The phases of the eukaryotic cell cycle are interphase, mitosis and cytokinesis. Interphase is further divided into G1
when a cell grows, S when the chromosomes are replicated, and G2 when the cell readies itself for cell division by
growing and making copies of various cell organelles. The chromosomes are divided equally during mitosis, followed by
cytokinesis when the new cell membrane forms around the two new daughter cells.
OBJECTIVE
Explain in detail how mitosis proceeds followed by cytokinesis.
Mitosis is divided into five stages: prophase, prometaphase, metaphase, anaphase, and telophase. During prophase,
chromosomes condense and the mitotic spindle begins to take shape. During prometaphase, the nuclear envelope
breaks down and the mitotic spindle expands. During metaphase, chromosomes line up in the middle of the cell with
sister chromatids facing opposite ends of the cell. During anaphase, sister chromatids separate, and motor proteins
move them along microtubules to opposite ends of the cell. During telophase, two new nuclei form, completing mitosis.
Shortly after the end of mitosis in animal cells, proteins form a ring around the middle of the cell and tighten into a noose,
separating the cytoplasm and cell membranes into two cells. This process is called cytokinesis.
OBJECTIVE
Describe how prokaryotes divide by binary fission.
Prokaryotic cell division commonly occurs by binary fission. This process results in replication of the single circular
chromosome and cytoplasm expansion. The cell membrane pinches together to form two new cells, each with a
complete genome. Cell division typically results in two daughter cells identical to the parent cell. Under certain
conditions, prokaryotes may reproduce using endospores, budding or multiple fission events with little growth between
them.
Key Terms
anaphase
Shortest stage of mitosis: proteins of the centromere linking the chromatids cut apart and the sister chromatids
separate.
binary fission
Cell division in prokaryotes where two daughter cells are produced from the parent cell; asexual reproduction in
unicellular prokaryotes and eukaryotes.
cell cycle
Life cycle of a cell; includes interphase, mitosis, and cytokinesis.
cell division
Reproduction of the cell in which one cell becomes two identical cells.
cell plate
The precursor for the new cell wall that forms during cytokinesis in plant cells.
centromere
DNA­protein complex which attaches the two sister chromatids.
centrosome
Organizes the microtubules of the spindle during mitosis in animals.
chromatin
DNA and proteins (histones) that make up the chromosomes.
chromosome
Tightly coiled form of the DNA­protein complex.
cleavage furrow
During cytokinesis in animals, the contractible ring of microfilaments around the equator of the cell.
cytokinesis
Division and separation of the cell outside the nucleus.
G0 phase
Extended, non­dividing stage in cells that divide infrequently.
G1 phase
First gap phase of interphase, when cell growth occurs.
G2 phase
Second gap phase when the cell continues to grow and prepares for division.
interphase
Phase of the cell cycle in which the cell grows and the DNA replicates.
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kinetochore
Protein structure associated with a specific DNA sequence that attaches the chromosome to a fiber of the spindle
apparatus.
M phase
Mitotic phase of the cell cycle.
meiosis
Type of cell division that produces gametes (in animals) or sexual spores (in fungi and plants) that have half the
genetic material of the parent cell.
metaphase
Stage of mitosis in which motor proteins move the chromosomes to align along the equator of the cell.
metaphase plate
An imaginary plane located at right angles to the mitotic spindle and midway between the spindle poles, where
chromosomes are positioned at metaphase.
mitosis
Type of cell division which results in two genetically identical cells.
mitotic spindle
Microtubules and associated proteins that attach to and move the chromosomes during cell division.
motor proteins
Proteins that convert the energy of ATP into movement along a surface. During mitosis and cytokinesis, motor
proteins move along microtubules and actin microfilaments facilitating the movement of things like chromosomes.
prometaphase
Stage of mitosis in which chromosomes condense further and attach to the spindle via the kinetochore.
prophase
Stage of mitosis in which the DNA condenses and chromosomes become visible.
S phase
Synthesis phase of interphase when the chromosomes are duplicated.
sister chromatid
One of a pair of chromatin threads; one side of a chromosome X­shape.
supercoiling
A process of compacting DNA inside a cell by twisting it around itself.
telophase
Stage of mitosis in which the nuclei reform and the chromosomes uncoil; microtubules make the spindle
dissociate.
tubulin
The building blocks or subunits of microtubules.
IN THIS MODULE
Overview of Cell Division
Prokaryotic Cell Division
Eukaryotic Cell Division
Summary
Test Your Knowledge
WHY DOES THIS TOPIC MATTER?
Cancer: What's Old Is New Again
Is cancer ancient, or is it largely a
product of modern times? Can
cutting­edge research lead to prevention
and treatment strategies that could make
cancer obsolete?
Synthetic Biology: Making Life from
Bits and Pieces
Scientists are combining biology and
engineering to change the world.
Stem Cells
Stem cells are powerful tools in
biology and medicine. What can
scientists do with these cells and their
incredible potential?
PRIMARY LITERATURE
The memory of iPS cells
Incomplete DNA methylation underlies a
transcriptional memory of somatic cells in
human iPS cells.
View | Download
http://www.nature.com/principles/ebooks/principles­of­biology­104015/29155678/4
2/3
1/20/2015
Summary of Cell Division | Principles of Biology from Nature Education
Genetically­matched iPS cells
more immunogenic than ES cells
Immunogenicity of induced pluripotent stem
cells.
View | Download
Adaptor proteins regulate cell
signaling
Structural basis for regulation of the Crk
signaling protein by a proline switch.
View | Download
The role of cyclin D1 in DNA repair
linked to cancer growth
A function for cyclin D1 in DNA repair
uncovered by protein interactome analyses
in human cancers.
View | Download
SCIENCE ON THE WEB
A View Through a Microscope
Watch a short video of cell division in
different types of cells.
A Population of Mitotic Cells
Watch cells dividing in a developing
embryo, and follow the fluorescently­
labeled spindles
Bacteria Dividing
See how bacterial division creates a
colony, starting from a few cells
Dividing Cancer Cells
How long does it take for cancer cells to
grow? Choose your time window and watch
what happens.
page 172 of 989
1 pages left in this module
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3/3
1/20/2015
Cell Division | Principles of Biology from Nature Education
Principles of Biology
contents
32 Cell Division
IN THIS MODULE
Overview of Cell Division
Test Your Knowledge
Prokaryotic Cell Division
Eukaryotic Cell Division
1. Under favorable environmental conditions, how do most prokaryotes reproduce?
Summary
Test Your Knowledge
meiosis
mitosis
endospores
budding
binary fission
WHY DOES THIS TOPIC MATTER?
Cancer: What's Old Is New Again
Is cancer ancient, or is it largely a
product of modern times? Can
cutting­edge research lead to prevention
and treatment strategies that could make
cancer obsolete?
2. How does cytokinesis begin in an animal cell?
Actin forms a ring outside the cell membrane.
Vesicles move to the middle of the cell.
Chromosomes line up across the middle of the cell.
A cell plate forms.
A cleavage furrow forms.
Synthetic Biology: Making Life from
Bits and Pieces
Scientists are combining biology and
engineering to change the world.
Stem Cells
Stem cells are powerful tools in
biology and medicine. What can
scientists do with these cells and their
incredible potential?
3. What is the role of centrosomes in mitosis?
holding together the two sister chromatids
organizing the microtubules that form the mitotic spindle
acting as an attachment point between microtubules and chromosomes
proofreading DNA
producing RNA and ribosomes
PRIMARY LITERATURE
The memory of iPS cells
Incomplete DNA methylation underlies a
transcriptional memory of somatic cells in
human iPS cells.
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4. Without the mitotic spindle, how would mitosis be different?
Genetically­matched iPS cells
more immunogenic than ES cells
Immunogenicity of induced pluripotent stem
cells.
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The cell membrane would not form around daughter nuclei.
Crossing over would not occur, so genes would more often segregate independently.
Sister chromatids would have to physically segregate by some other means.
More mistakes would occur during DNA replication.
DNA synthesis would be incomplete.
Adaptor proteins regulate cell
signaling
Structural basis for regulation of the Crk
signaling protein by a proline switch.
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5. How is DNA arranged in a eukaryotic cell during the G1 phase of interphase?
The role of cyclin D1 in DNA repair
linked to cancer growth
A function for cyclin D1 in DNA repair
uncovered by protein interactome analyses
in human cancers.
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in pairs of sister chromatids
in plasmids
by microtubule length
in chromatin fibers
in condensed chromosomes
SCIENCE ON THE WEB
A View Through a Microscope
Watch a short video of cell division in
different types of cells.
6. In which phase does a normal cell make the commitment to divide or not?
G1
M
G2
S
None of these answers are correct.
A Population of Mitotic Cells
Watch cells dividing in a developing
embryo, and follow the fluorescently­
labeled spindles
Bacteria Dividing
See how bacterial division creates a
colony, starting from a few cells
7. Which of the following steps of mitosis occurs first in plants and animals?
Dividing Cancer Cells
How long does it take for cancer cells to
grow? Choose your time window and watch
what happens.
The DNA replicates.
Chromatids line up in the middle of the cell.
The nuclear membrane breaks apart.
Sister chromatids separate.
The cell membrane pinches together in the middle.
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