Important words and concepts from Chapter 12,
Campbell & Reece, 2002 (1/29/2005):
by Stephen T. Abedon (abedon.1@osu.edu)
for Biology 113 at the Ohio State University
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(1) Chapter title: The Cell Cycle
(a)
[The Cell Cycle (Google Search)] [the cell cycle and mitosis
tutorial (The Biology Project)]
[index]
(a)
The goal of cell division typically is to equally partition two
more-or-less identical copies of genetic material between two daughter cells
(b)
Additionally, cytoplasm is divided between the two
daughter cells, usually more-or-less equally between them
(c)
There exist numerous variations on cell division, though for our
purposes we can divide these up into those that involve:
(i)
Binary fission (considered also in
(ii)
Mitosis (the emphasis of this chapter) vs.
(iii)
Meiosis (the
emphasis of chapter 13)
(d)
[cell division (Google Search)] [index]
(a)
One meaning of genome is the sum of genetic material within a cell,
just following division (i.e., before the next round of genome
replication)
(b)
(Your genome consists of 46 separate chromosomes of 22 autosomal types
plus 1 or 2 sex chromosome types; the genome of a bacterium consists of one
closed-circular chromosome)
(c)
[genome (Google Search)] [index]
(a)
Chromatin is a complex of DNA and protein
(b)
Chromatin is not visible, as individual chromosomal entities, through a
light microscope
(c)
Prior to cell division (M phase) a eukaryotic cell’s genome consists of chromatin
(d)
[chromatin (Google Search)] [chromatin links (MicroDude)]
[index]
(a)
Genomes in eukaryotes are made
up of individual DNA duplexes (double helices)
(b)
The human genome contains 46 of these duplexes
(c)
During cell division each of these individual chromatin
condense into a light-microscope-visible structure called
a chromosome
(d)
That is, eukaryote chromosomes are DNA-protein complexes which,
contrasting with chromatin, are visible as individual entities
through a light microscope
(e)
See Figure 12.3, Chromosome
duplication and distribution during mitosis
(f)
[chromosome or chromosomes
(Google Search)] [index]
(6)
Sister chromatids (sister chromatid pairs)
(a)
Following the replication of a chromatin fiber
(i.e., double helix), each pair of double helices is
known as a sister chromatid pair
(b)
Each individual double helix is known as a sister chromatid
(c)
Note that, at this point, sister chromatids are still not visible, as
distinct entities, through a light microscope
(d)
See Figure 12.3, Chromosome
duplication and distribution during mitosis
(e)
Start to think in terms of putting in some effort to understand the
difference (as well as the similarities) between the terms chromatin, double helix, sister chromatid, sister chromatid pair, and chromosome;
being able to properly name the DNA at different
points in the cell cycle is one means by which I can assess your understanding
of mitosis
(and meiosis)
(f)
[sister chromatid or chromatids
(Google Search)] [index]
(a)
The two sister chromatids remain bound to one another through a
region of DNA/protein
called a centromere, forming a sister chromatid pair
(b)
See Figure 12.3, Chromosome
duplication and distribution during mitosis
(c)
[centromere (Google Search)] [index]
(a)
The division of a eukaryotic cell is
commonly divided into a number of phases of cell division,
together called the cell cycle
(b)
These division, at a gross level, include:
(i)
Interphase
(ii)
M phase
(c)
See Figure 12.4, The cell
cycle
(d)
[cell cycle (Google Search)] [the plant cell cycle
(Plant Biology 101—Ohio State
University)] [index]
(9) Interphase (gap phases of interphase, S phase of interphase, synthesis phase of interphase)
(a)
Interphase is further divided as follows:
(i)
G1 phase (first gap)
(ii)
S phase (synthesis)
(iii)
G2 phase (second gap)
(b)
See Figure 12.4, The cell
cycle
(c)
S phase is the time during which DNA replication occurs
(d)
The G phases are times during which no DNA replication is occurring and
mitosis (M phase) is not occurring
(e)
Note that typically the majority of a cell’s cycle is
spent in interphase
(f)
During interphase a cell is synthesizing proteins, making organelles, and basically doing whatever it is that cells do,
other than dividing
(g)
[interphase cell, gap phase, S phase cell, synthesis phase cell
(Google Search)] [index]
(a)
During M phase the cell undergoes:
(ii)
Cytokinesis
(b)
See Figure 12.4, The cell
cycle
(c)
[M phase cell (Google Search)] [mitosis (Caduceus MCAT Review)]
[index]
(a)
Mitosis is the division of a cell’s nucleus (not
the overall division of a cell, only part of that overall
division)
(b)
The goal of mitosis is the equal partitioning of two more-or-less
identical genomes into each of two daughter-cell nuclei
(c)
Mitosis occurs in five reasonably well-defined phases (PPMAT)
(i)
Prophase
(ii)
Prometaphase
(iii)
Metaphase
(iv)
Anaphase
(v)
Telophase
(d)
See Figure 12.5, The stages
of mitotic cell division in an animal cell
(e)
Note that I have an expectation that you will basically learn (i.e.,
memorize and understand) Figure 12.5 of your text
(f)
[mitosis (Google Search)] [index]
(a)
The gap phase just prior to mitosis is called G2
(b)
Note that by G2, by definition, the DNA
is already replicated and
consists of sister chromatid
pairs
(c)
Note also that the cell’s centrosomes
are also already replicated so that the cell in G2 phase contains
two identical centrosomes sitting side-by-side, external to the nucleus
(d)
See Figure 12.5, The stages
of mitotic cell division in an animal cell
(e)
Other characteristics of the G2 phase include
(i)
Nuclear membrane is intact
(ii)
Genome is not visible through a light microscope (i.e., the chromatin has not
yet condensed to form chromosomes)
(iii)
Nucleoli are visible
(f)
[g2 of interphase (Google Search)] [index]
(a)
Centrosomes
consist of two centrioles
(b)
See Figure 12.5, The stages
of mitotic cell division in an animal cell
(c)
External to the centrosome exists a star-like array of microtubules called an aster
(d)
Recall that the centrosome is the center of the microtubule array of a
cell
(e)
Also try to keep in mind that the term centrosome
is not a synonym of the term centromere (nor, for that matter, is
centrosome an exact synonym of centriole)
(f)
FAQ: In
(g)
[centrosome or centrosomes
(Google Search)] [index]
(a)
Nuclear division commences during prophase
(b)
See Figure 12.5, The stages
of mitotic cell division in an animal cell
(c)
Also during prophase the centrosomes move to
opposite poles of the cell along the still-intact nuclear membrane
(d)
Forming between the centrosomes are overlapping microtubules called mitotic spindles
(e)
These mitotic spindles are responsible for propelling the centrosomes
away from each other to opposite poles of the cell
(f)
Additional characteristics of prophase include
(i)
Chromatin begins to condense into chromosomes, becoming visible through the light microscope
(ii)
Chromosomes are visibly
connected at their centromeres
(iii)
Nucleoli disappear
(g)
[prophase (Google Search)] [index]
(a)
Characteristics of prometaphase include
(i)
Nuclear membrane disappears
(ii)
Mitotic spindles invade what had been the
nuclear region
(iii)
Chromosomes fully condense from chromatin
(iv)
Centrosomes fully reach the poles of the cell
(v)
Some of the mitotic spindle microtubules attach
to the centromeres of the sister chromatid pairs
(vi)
Sister chromatid pairs are visibly jerked about (as seen through a
light microscope) by the attached mitotic spindles
(b)
See Figure 12.5, The stages
of mitotic cell division in an animal cell
(c)
[prometaphase (Google Search)] [index]
(a)
Kinetochores are proteinaceous region adjacent to the centromere
of a sister chromatid pair
(b)
Kinetochores do the interacting with the mitotic spindles
(c)
The mitotic spindles with which kinetochores interact are called kinetochore microtubules
(d)
See Figure 12.6, The mitotic
spindle at metaphase
(e)
See Figure 12.7, Testing a
hypothesis for chromosome migration during anaphase
(f)
[kinetochore (Google Search)] [index]
(a)
During prometaphase the spindle fibers tug back and forth on sister chromatids
(b)
Ultimately the tugs even out such that sister chromatids are now
located within a plane representing a perpendicular cross section of the cell
(c)
See Figure 12.5, The stages
of mitotic cell division in an animal cell
(d)
This plane is not a physical object but instead represents where the
sister chromatids are lined up, equidistant from the poles of the cell (and
from the centrosomes)
(e)
At this point the cell is said to be in metaphase
(f)
[metaphase (Google Search)] [index]
(a)
The metaphorical plane at the center of the cell upon which the chromosomes are lined up during metaphase is called the metaphase plate
(b)
See Figure 12.5, The stages
of mitotic cell division in an animal cell
(c)
See Figure 12.6, The mitotic
spindle at metaphase
(d)
[metaphase plate (Google Search)] [index]
(a)
The complex structure consisting of the microtubules and centrosomes together are called
the spindle (mitotic
spindle)
(b)
See Figure 12.5, The stages
of mitotic cell division in an animal cell
(c)
See Figure 12.6, The mitotic
spindle at metaphase
(d)
[spindle mitosis (Google Search)] [index]
(a)
Metaphase ends when chromosomes begin
to be pulled toward the centrosomes, separating sister chromatids from one another
(b)
At this point the dividing cell has entered anaphase
(c)
See Figure 12.5, The stages
of mitotic cell division in an animal cell
(d)
Note that during anaphase the chromosomes are being dragged by the kinetochore microtubules by their centromeres
(e)
Note that this method of separation of chromosomes assures that one of
each type of chromosome (and only one) is transferred to each of the two
daughter-cells-to-be
(f)
The cell is also lengthening during anaphase
(g)
[anaphase (Google Search)] [index]
(a)
Telophase begins upon the completion of the chromosome’s anaphase
journey
(b)
See Figure 12.5, The stages
of mitotic cell division in an animal cell
(c)
With telophase
(i)
Chromosomes de-condense back into chromatin
(ii)
Nuclear membrane reforms
(iii)
Nucleoli reappear
(d)
[telophase (Google Search)] [index]
(a)
Microtubules of the normal cell cytoskeleton are disassembled upon cell division
(b)
These microtubules are then reassembled associated with the now two centrosomes
present when M phase begins
(c)
(that is, when the mother cell had a single centrosome, these
microtubules were associated with that single centrosome, but now these
microtubules need to be rearranged to become associated with the centrosome of
each of the two daughter cells)
(d)
An immediate role of these newly-formed microtubules is in the mitotic
process
(e)
In this guise the microtubules, along with the two polar centrosomes
(e.g., during metaphase), are called the mitotic spindle
(f)
See Figure 12.6, The mitotic
spindle at metaphase
(g)
[mitotic spindle or spindles
(Google Search)] [index]
(23) Mitotic
microtubule nomenclature
(a)
The microtubules observed during mitosis
include
(ii)
Nonkinetochore
microtubules
(iii)
Aster
“microtubules”
(iv)
Spindle fibers
(b)
See Figure 12.6, The mitotic
spindle at metaphase
(c)
[mitotic microtubule or
microtubules (Google Search)] [index]
(a)
Bundles of microtubules attached to the centromeres
of chromosomes are called spindle fibers
(b)
Spindle fibers are large enough to be observed through a light microscope
(c)
Presumably spindle fibers are a form (or grouping) of kinetochore microtubules
(d)
See Figure 12.6, The mitotic
spindle at metaphase
(e)
[spindle fiber or fibers
(Google Search)] [index]
(a)
The microtubules of the aster presumably help
anchor the centrosome
(b)
The centrosome thus can serve as an anchor for the movement of chromosomes during anaphase
(c)
See Figure 12.6, The mitotic
spindle at metaphase
(d)
[aster microtubule or
microtubules (Google Search)] [index]
(26) Nonkinetochore
microtubules
(a)
The nonkinetochore microtubules overlap at the metaphase
plate
(b)
Instead of helping to move chromosomes toward centrosomes, the nonkinetochore
microtubules serve to push the centrosomes away from one another during anaphase,
thus lengthening the still-to-be-divided cell
(c)
This pushing away presumably is very similar to how the centrosomes
moved toward the poles of the cell during prophase
(d)
See Figure 12.6, The mitotic
spindle at metaphase
(e)
[nonkinetichore microtubules
(Google Search)] [index]
(a)
These are the microtubules that
the kinetochores of the chromosomes interact with
(b)
See Figure 11.7
(c)
Think of the kinetochore as a tiny
tractor that hauls its chromosome load down the kinetochore microtubule, toward
the centrosome
(d)
As the kinetochore moves, the tubulin subunits are liberated from the side of the
kinetochore that is away from the centrosome
(e)
See Figure 12.6, The mitotic
spindle at metaphase
(f)
See Figure 12.7, Testing a
hypothesis for chromosome migration during anaphase
(g)
FAQ: Are mitotic spindles,
kinetochore microtubules, and spindle fibers all connected, in other words do
they all do the same task? The mitotic spindle includes more than just the
kinetichore microtubules (i.e., the non-kinetichore microtubules are also
included among the mitotic spindle, which makes sense since the non-kinetichore
microtubules also have a role in mitosis and meiosis). Spindle fibers are
microtubules that are gathered together in sufficiently large bundles that they
are visible through the light microscope. Again, it is important to take a
historical view. The spindle fibers and mitotic spindle were discovered before
kinetichore microtubules because the spindle fibers are visible through a light
microscope. It was only later that it was found that the microtubles of the
mitotic spindle consist of at least two types, those connected to chromosomes
(kinetichore microtubules) and those that are not. For that matter, it was only
later that it was understood that the fibers of the mitotic spindle are
microtubules.
(h)
[kinetichore microtubules
(Google Search)] [index]
(a)
Cytokinesis is the division of the cytoplasm
(b)
Note that cytokinesis is only the final phase of cell
division, not synonymous with cell division, because cell division
minimally requires DNA replication plus genome segregation
(c)
See Figure 12.5, The stages
of mitotic cell division in an animal cell
(d)
Cytokinesis can occur more or less simultaneous to telophase
(e)
Note, nevertheless, that the division of the nucleus and the division
of the cytoplasm are two separate events
(f)
There are many situations in which cytokinesis does
not follow mitosis, thus resulting in multinucleated cells (e.g., our
muscle cells)
(g)
Note also that cytokinesis does not control the segregation of the
cytoplasmic contents
(h)
Instead, the cytoplasm is divided with the assumption
that necessary components will end up in both cells and/or may be manufactured
following cytokinesis
(i)
See Figure 12.8, Cytokinesis
in animal and plant cells
(j)
[cytokinesis (Google Search)] [index]
(a)
The cytokinesis
of an animal cell involves the formation of a cleavage furrow
(b)
See Figure 12.8a,
Cytokinesis in animal and plant cells
(c)
This is caused by a sub-plasma-membrane band of microfilaments (actin) that is found at the perimeter of the metaphase
plate
(d)
The shortening of this band causes the plasma membrane to invaginate around the
midline of the cell
(e)
Ultimately this leads to a complete separation of the two cells
(f)
[cleavage furrow (Google Search)] [index]
(30) Mitosis and
multicellularity
(a)
In single-celled eukaryotic organisms, mitosis is non-sexual (asexual) reproduction
(b)
In multicelled eukaryotes, mitosis is the cell division that
allows the organism to increase in cell number, which is associated with
increases in organismal size
(c)
In addition, in multicelled organisms mitosis is involved
in tissue repair and replacement
(d)
In other words, mitosis is how we make more of our bodies (though not
how we make our sperm nor our egg cells)
(e)
[mitosis and multicellularity
(Google Search)] [index]
(a)
There exist a variety of mechanisms that allow an individual cell to
control its own division (see, for example, pp. 214-218 of your
text)
(b)
These mechanisms can be both positive and negative, i.e., there exist
some signals that must be present and other signals that must be absent for
cell division to proceed
(c)
Typically the cell cycle gets stuck in G1 phase if signals for cell division to proceed
are not present
(d)
Once the cell cycle proceeds to S phase, the cell
is committed to reproducing (i.e., are committed to proceeding through M phase
and cytokinesis)
(e)
Genes associated with various mechanisms of
restraint of cell growth are called oncogenes (etc.) if they have been mutated
to a lack of cell-growth-restrain
(f)
Mechanisms of restraint include
(i)
Lack of ability to divide indefinitely (are not immortal)
(ii)
Lack of ability to divide when in contact on all sides by other cells
(iii)
Lack of ability to divide in the absence of extracellular growth
factors
(iv)
Etc.
(g)
[control of cell division
(Google Search)] [index]
(a)
Prokaryotes divide by a relatively simple
mechanism of cell division called binary fission
(b)
Partitioning of genetic material is achieved through
(i)
The attachment of the bacterial chromosome
to the cell membrane
(ii)
A lengthening of the cell by the deposition of new membrane and cell wall material between the two chromosomes
(c)
See Figure 12.10, Bacterial
cell division (binary fission)
(d)
Separation of the genetic material is followed by division of the cytoplasm
(e)
Note in the figure that the two daughter cells are essentially
identical to the parent cell at the top of the figure
(f)
[binary fission (Google Search)] [binary fission links
(MicroDude)]
[index]
(33)
(If there is time, I will introduce
probability theory which otherwise is found in
chapter 14)
(34) Cancer [this cancer discussion is supplemental]
(a)
What follows is a discussion of cancer, a manifestation of
out-of-control mitotic division within a multicellular organism, that is
written from an evolutionary ecological perspective
(b)
You will not be held responsible for learning this material; the
material also has not been recently edited; we may or may not get to this
material during lecture
(c)
[cancer (Google Search)] [index]
(35)
Non-genetic identity and
defection
(a)
If individual cells of a multicelled organism are not genetically
identical, then the reproductive success of one cell does not automatically
correspond to the reproductive success of any other cell
(b)
Such situations destabilize cooperative behavior between cells
(c)
An extreme example is a lack of cooperation displayed by an unrelated
pathogen
(36)
Mechanisms assuring
cooperation
(a)
Multicelled organisms have evolved a variety of mechanisms that cause
genetically identical cells to act cooperatively
(b)
They have also evolved mechanisms which serve to prevent
non-genetically identical cells from acting not cooperatively
(c)
Finally, they have evolved mechanisms that serve to prevent
non-genetically identical cells from arising at all
(d)
These mechanisms include
(i)
Individual cell division restraint
(ii)
Immune system control
(iii)
Mechanisms which combat mutation
(iv)
Starting babies with one or few cells
(v)
Requirement for functionality in baby-generating tissue
(37)
Immune system control
(a)
Body cells that have managed to escape their own self-imposed
restraints on cell division often come to not resemble other body cells, at
least to the “eyes” of the immune system
(b)
Often these cells are reproducing at either developmentally
inappropriate times, or in inappropriate positions in the body
(c)
Most such cells are recognized by the immune system and destroyed
(d)
[controlling cancer immune
system (Google Search)] [index]
(38)
Combating mutation
(a)
Lack of genetic identity results from mutation within individual cells
(b)
Oncogenes (cancer-causing genes) are examples of what can result from
the occurrence of mutation
(c)
Cells possess elaborate mechanisms that usually serve to significantly
minimize the occurrence of genetic change
(d)
(the absence of such mechanisms themselves are products of
cancer-contributing, mutated genes)
(e)
We will consider these mechanism in Chapter 16
(39)
Starting from few cells
(a)
A typically overlooked mechanism by which the genetic identity of a
multicellular organism is maintained is via the initiation of the organism
starting with only a single cell
(b)
This assures that all of the cells associated with that organism are
identical from the start
(c)
The alternative mechanism, starting new organisms from many cells,
allows any evolution that had occurred in the parent organism (i.e.,
over-replication of renegade cells) to continue in the offspring
(d)
Thus, starting babies from only a single cell actually serves as a
cancer-fighting strategy, and in fact, in part helps explain (to some degree)
why older people are typically more prone to cancer than are younger people
(e)
Note that this mechanism is equivalent, both in terms of execution and
utility, to pure culture technique as employed in microbiology
(40)
Minimal functionality
(a)
Finally, mutational corruption is minimized by the requirement for some
minimal biological functionality in both baby generating tissue (e.g., the
gonads in animals) and in the tissue of the progeny offspring
(b)
Typically, defects in either eggs, sperm, or genitalia result in
offspring (or germ cell) non-viability
(c)
Certainly partially defective genitalia (say one gonad versus the other
in humans) may have a reduced potential to contribute germ cells (i.e., eggs or
sperm) relative to healthy tissue, and thus have a reduced potential to compete
with the non-mutationally aberrant cells of the parent organism
(d)
This is especially a concern for plants which, unlike many animals,
fail to sequester the cells they use to produce the next generation
(e)
However, for a mutationally aberrant plant cell to give rise to a
progeny plant, that cell must be sufficiently intact to, for example, give rise
to a properly functioning flower
(f)
Thus, plant mutational aberration, though it may be more tolerated than
mutational aberration among animal cells, nevertheless must meet some minimal
level of functionality to compete with the parent plant over contributing to
the next generation
(41)
Tumors
(a)
The emergence and destructiveness of cancer occurs within a backdrop of
such evolutionary games as those just discussed
(b)
The idea is that a cell which divides more rapidly can out-compete less
rapidly dividing cells
(c)
More rapid division can stem from mutational deviation from the norm
(d)
A more rapidly dividing cell, among solid tissue, will, if left alone
by the immune system, produce a tumor
(e)
A tumor is an relatively undifferentiated mass of cells that is better
at growing than it is at contributing to the health of the parent organism
(f)
Most tumors are not harmful unless they are allowed to progress to
large dimensions
(g)
Then they can mechanically disrupt normal body function (in addition to
stealing body nutrients)
(h)
[tumor or tumors (Google Search)] [index]
(42)
Invasiveness
(a)
One thing that can contribute to tumor growth is a mutationally
acquired tendency toward invasiveness
(b)
Such tumors tend to invade surrounding tissue
(c)
This makes such tumors more disruptive than non-invasive tumors
(d)
[tumor invasiveness
(Google Search)] [index]
(43)
Benign tumor
(a)
A tumor that is not invasive is described as benign
(b)
Benign tumors typically are sheathed in connective tissue
(c)
[benign tumor (Google Search)] [index]
(44)
Malignant tumor
(a)
A tumor that is invasive is described as malignant
(b)
Another name for malignant tumors is cancerous
(c)
[malignant tumor (Google Search)] [index]
(45)
Metastasis
(a)
Cancerous tumors are not too big a deal if they stay in one place
(b)
Their removal will require a removal of surrounding tissue since cancerous
tumors will be expected to have invaded surrounding tissue
(c)
But so long as the entire tumor has remained a single hunk of tissue,
treatment can be relatively easy (the exception being when the tumor has
invaded tissue which is sufficiently vital to body functioning that it cannot
be easily removed)
(d)
The bigger problem with cancerous tumors occurs when some cancer cells
mutationally lose their ability to remain attached to the primary tumor mass
(e)
These cells can migrate into the circulatory system
(f)
Other mutations can allow such cells to reemerge from the circulatory
system at other locals and found secondary tumors
(g)
This process is called metastasis
(h)
[metastasis, metastasize (Google Search)] [index]
(46)
Tumor size and cancer
severity
(a)
As tumors grow they tend to mutate (dividing cells mutate more readily
than non-dividing cells)
(i)
Tumor size tends to be directly proportion to cell number
(ii)
Cell number is directly proportional to the number of cell divisions
which have occurred
(iii)
The number of mutations that have occurred is directly proportional to
the number of cell divisions which have occurred
(iv)
Invasiveness, metastasis, and other nasty properties of cancer cells
(such as anti-cancer drug resistance) occur with mutational change
(b)
Thus, the larger a tumor is, the more likely it has evolved to invade
other tissue, move to other parts of the body, and house cells that are already
(i.e., before treatment even commences) resistant to anti-cancer drugs
(c)
This is why it is typically considered to be “good” when tumors are
“caught early”
(d)
Note, however, that it takes a long time for cell division to occur and
mutational change to accumulate; this is why cancers tend to start years or
even decades before they are detected
(e)
Note additionally that the rate of cancer growth is proportional to
cancer cell number, i.e., bigger tumors grow faster than smaller tumors (this
is a consequence of the properties of exponential growth)
(f)
Thus, very often a person may live with a cancer for years or even
decades, yet die only a few months following diagnosis; very often diagnosis
isn’t made until tumors are large, and large tumors grow larger very fast and
are more likely to have metastasized
(g)
[tumor size and cancer severity
(Google Search)] [index]
(47)
Vocabulary [index]
(a)
Anaphase
(b)
Aster
(c)
Binary fission
(d)
Cell cycle
(e)
Cell division
(f)
Centromere
(g)
Centrosomes
(h)
Chromatin
(i)
Chromosome
(j)
Cleavage furrow
(l)
Cytokinesis
(m)
G2 of interphase
(o)
Genome
(p)
Interphase
(q)
Kinetochore
(s)
M phase
(t)
Metaphase
(u)
Metaphase plate
(v)
Mitosis
(w)
Mitosis and multicellularity
(x)
Mitotic microtubule nomenclature
(y)
Mitotic spindle
(z)
Nonkinetochore
microtubules
(aa)
Prometaphase
(bb)
Prophase
(dd)
Sister
chromatids
(ff)
Spindle
(gg)
Spindle fibers
(hh)
Synthesis phase of interphase
(ii)
Telophase