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]

(2) Cell division (see also cell division)

(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 Ch. 18) vs.

(ii)                   Mitosis (the emphasis of this chapter) vs.

(iii)                 Meiosis (the emphasis of chapter 13)

(d)                   [cell division (Google Search)] [index]

 

VARIOUS NAMES FOR DNA-CONTAINING STRUCTURES

 

(3) Genome (see also genome)

(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 most bacteria consists of one closed-circular chromosome)

(c)                    [genome (Google Search)] [index]

(4) Chromatin (see also chromatin)

(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]

(5) Chromosome (see also chromosome)

(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, Chromosome duplication and distribution during mitosis

(f)                     [chromosome or chromosomes (Google Search)] [index]

(6) Sister chromatids (sister chromatid pairs) (see also sister chromatid pair and sister chromatid pair)

(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, 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]

(7) Centromere (see also centromere)

(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, Chromosome duplication and distribution during mitosis

(c)                    [centromere (Google Search)] [index]

 

CELL CYCLE

 

(8) Cell cycle (see also cell cycle)

(a)                    The division of a eukaryotic cell is commonly divided into a number of phases of cell division, together called the cell cycle

(b)                    Thus division, at a gross level, includes:

(i)                     Interphase

(ii)                   M phase

(c)                    See Figure, The cell cycle

(d)                   [cell cycle (Google Search)] [index]

(9) Interphase (gap phases of interphase, S phase of interphase, synthesis phase of interphase) (see also interphase, gap phase, G0, G1, G2, and S phase)

(a)                    Interphase is further divided as follows:

(i)                     G1 phase (first gap)

(ii)                   S phase (synthesis)

(iii)                 G2 phase (second gap)

(b)                   See Figure, 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]

(10) G2 of interphase (see also G2)

(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, 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]

(11) M phase (see also M phase)

(a)                    During M phase the cell undergoes:

(i)                     Mitosis

(ii)                   Cytokinesis

(b)                   See Figure, The cell cycle

(c)                    [M phase cell (Google Search)] [index]

(12) Control of cell division

(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]

(13) Mitosis and multicellularity

(a)                    Keep in mind in the following discussion that mitosis is not equivalent to cell division; instead it represents nuclear division; nevertheless, to distinguish the cell division that is associated with mitosis from that which is associated with meiosis, it is common to use a shorthand called mitotic division, meaning cell division that is underlain by mitosis (rather than meiosis)

(b)                    In single-celled eukaryotic organisms, mitosis forms the basis of non-sexual (asexual) reproduction

(c)                    In multicelled eukaryotes, mitosis underlies the cell division that allows the organism to increase in cell number, which is associated with increases in organismal size

(d)                   In addition, in multicelled organisms mitosis (i.e., mitotic ell division) is involved in tissue repair and replacement

(e)                    In other words, mitosis is how we make more of our bodies (though not how we make our sperm nor our egg cells)

(f)                     [mitosis and multicellularity (Google Search)] [index]

(14) Binary fission (see also binary fission)

(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, 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)] [index]

 

STRUCTURES ASSOCIATED WITH MITOSIS

 

(15) Mitotic microtubule nomenclature

(a)                    The microtubules observed during mitosis include

(i)                     Kinetochore microtubules

(ii)                   Nonkinetochore microtubules

(iii)                 Aster "microtubules"

(iv)                 Spindle fibers

(b)                    Centrosomes are also composed of and associated with microtubules

(c)                    See Figure, The mitotic spindle at metaphase

(d)                   [mitotic microtubule or microtubules (Google Search)] [index]

(16) Centrosomes (see also centrosome)

(a)                    Centrosomes consist of two centrioles

(b)                   See Figure, 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 Ch. 12 there are a lot of c-words, could you explain the difference between, centrosomes, centromere, sister chromatids, chromosomes, and chromatin? A centrosome is the center of the microtubular array of the cytoskeleton. A centrosome consists of two, perpendicularly arrayed centrioles. A centromere is a region on the DNA/chromosome at which sister chromatids are joined and to which kinetochores are bound. A sister chromatid is one of two (a pair) of DNA double helices that result from the replication a single DNA double helix (as least as described in a eukaryotic cell). Sister chromatid pairs are joined at their centromeres. Chromosome has two meanings, one more ambiguous, one less so. The less ambiguous meaning is one or two DNA double helices, complexed with proteins, that is visible during mitosis or meiosis. So long as the centromeres of a sister chromatid pair remain attached, the visible pair is described as a chromosome. When anaphase of mitosis (or anaphase II of meiosis) begins, the sister chromatids are separated. Each of the now autonomous sister chromatids is now referred to as a chromosome. More ambiguous, the term chromosome is often used to describe chromatin fibers, i.e., DNA double helices other than those visible through a light microscope during mitosis or meiosis. The problem is that the visible things were discovered before the chromatin was (since, of course, the former are visible though a light microscope!) so chromosome has a technical meaning that is more precise than the tendency to use the term to describe all nuclear DNA as chromosomal, independent of its degree of condensation. Chromatin is less condensed and less organized than are chromosomes, using that term in its stricter sense. For a more visual description of the difference between chromatin and chromosomes, as well as what just what the condensation of chromatin into a chromosome is all about, see Figure of your text, page 353 [NOTE, PAGE NUMBER/FIGURE NUMBER MAY BE INCORRECT].

(g)                    [centrosome or centrosomes (Google Search)] [index]

(17) Spindle

(a)                    The complex structure consisting of the microtubules and centrosomes together are called the spindle (mitotic spindle)

(b)                   See Figure, The stages of mitotic cell division in an animal cell

(c)                    See Figure, The mitotic spindle at metaphase

(d)                   [spindle mitosis (Google Search)] [index]

(18) Mitotic spindle (see also mitotic spindle)

(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, The mitotic spindle at metaphase

(g)                    [mitotic spindle or spindles (Google Search)] [index]

(19) Spindle fibers (see also spindle fiber)

(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, The mitotic spindle at metaphase

(e)                    [spindle fiber or fibers (Google Search)] [index]

(20) Aster (see also aster)

(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, The mitotic spindle at metaphase

(d)                   [aster microtubule or microtubules (Google Search)] [index]

(21) Kinetochore (see also kinetochore)

(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, The mitotic spindle at metaphase

(e)                    See Figure, Testing a hypothesis for chromosome migration during anaphase

(f)                     [kinetochore (Google Search)] [index]

(22) Nonkinetochore microtubules (see also nonkinetochore microtubule)

(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, The mitotic spindle at metaphase

(e)                    [nonkinetochore microtubules (Google Search)] [index]

(23) Kinetochore microtubules (see also kinetochore microtubule)

(a)                    These are the microtubules that the kinetochores of the chromosomes interact with

(b)                   See Figure

(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, The mitotic spindle at metaphase

(f)                     See Figure, 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 kinetochore microtubules (i.e., the non-kinetochore microtubules are also included among the mitotic spindle, which makes sense since the non-kinetochore 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 kinetochore microtubules because the spindle fibers are visible through a light microscope. It was only later that it was found that the microtubules of the mitotic spindle consist of at least two types, those connected to chromosomes (kinetochore 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)                    [kinetochore microtubules (Google Search)] [index]

 

MITOSIS = NUCLEAR DIVISION

 

(24) Mitosis (see also mitosis)

(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, 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 of your text

(f)                     [mitosis (Google Search)] [index]

(25) Prophase (see also prophase)

(a)                    Nuclear division commences during prophase

(b)                   See Figure, 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]

(26) Prometaphase (see also prometaphase)

(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, The stages of mitotic cell division in an animal cell

(c)                    [prometaphase (Google Search)] [index]

(27) Metaphase (see also metaphase)

(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, 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]

(28) Metaphase plate (see also metaphase plate)

(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, The stages of mitotic cell division in an animal cell

(c)                    See Figure, The mitotic spindle at metaphase

(d)                   [metaphase plate (Google Search)] [index]

(29) Anaphase (see also anaphase)

(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, 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]

(30) Telophase (see also telophase)

(a)                    Telophase begins upon the completion of the chromosome's anaphase journey

(b)                   See Figure, 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]

 

CYTOKINESIS IS POST M-PHASE CYTOPLASMIC DIVISION

 

(31) Cytokinesis (see also cytokinesis)

(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, 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, Cytokinesis in animal and plant cells

(j)                      [cytokinesis (Google Search)] [index]

(32) Cleavage furrow (see also cleavage furrow)

(a)                    The cytokinesis of an animal cell involves the formation of a cleavage furrow

(b)                   See Figure, 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]

 

(33) (If there is time, I will introduce probability theory which otherwise is found in chapter 14)

 

ADDITIONAL MATERIALS (NOT RESPONSIBLE FOR)

 

 

(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]

 

VOCABULARY

 

(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

(k)                    Control of cell division

(l)                      Cytokinesis

(m)                  G2 of interphase

(n)                    Gap phases of interphase

(o)                    Genome

(p)                    Interphase

(q)                    Kinetochore

(r)                     Kinetochore microtubules

(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

(cc)                 S phase of interphase

(dd)               Sister chromatids

(ee)                 Sister chromatid pairs

(ff)                  Spindle

(gg)                Spindle fibers

(hh)                Synthesis phase of interphase

(ii)                    Telophase

(48) Practice questions [index]

(a)                    Contrast chromatin and chromosome in terms of visibility through a light microscope. To answer this question, assume that the word chromosome is not being employed ambiguously.

(b)                    What is binary fission?

(c)                    Matching: (a) telophase, (b) prometaphase, (c) anaphase, (d) prophase, (e) metaphase. Each item is not used more than once.

(i)                     metaphase plate __________

(ii)                   early mitotic spindle __________

(iii)                 nucleoli reappear _________

(iv)                 nuclear membrane fragments __________

(v)                   cell lengthens __________

(d)                   The cytoskeleton components most associated with cytokinesis are __________.

(i)                     Microtubules

(ii)                   Asters

(iii)                 Microfilaments

(iv)                 Kinetochores

(v)                   Intermediate filaments

(vi)                 Spindle fibers

(e)                    Typically, the cell cycle of a non-dividing cell is "stuck" in G1 of interphase if signals for cell division to proceed are not present. Once the cell cycle proceeds to __________ phase, however, the cell is committed to reproducing (i.e., undergoing mitosis)

(f)                     Draw and label a cell undergoing (i.e., in) anaphase of mitosis. The parent of this cell contained three double helices during G1 of interphase (yes, this cell is haploid). Be as thorough and as detailed as you can. Relative points will be gained for any and all relevant detail. Relative points will be lost for incorrect information.

(g)                    Beyond simply stating "nuclear division", what is the "goal" of the complex choreography of mitosis?

(h)                    What is a sister chromatid?

(i)                      A diploid cell has six double helices (three pairs) in G1 of interphase. Draw Metaphase, being sure to include the centrosome, the plasma membrane, kinetochore microtubules, non-kinetochore microtubules, centromeres, and the appropriate number of sister chromatid pairs. Be sure to indicate homologues by giving each "type" of homologue a unique identifier (i.e., "1", "2", etc.).

(j)                      The replication of a bacterial cell is called __________.

(k)                    How many individual molecules of DNA are there in one sister chromatid pair? (Recall that a single double helix consists of two individual molecules of DNA)

(l)                      Besides simply stating "nuclear division," what is the ultimate goal of the complex choreography we observe during mitosis?

(m)                  During what phase of mitosis do the centrosomes fully reach the poles of the cell?

(n)                    Fill in the blanks: The centrosome consists of two __________ and serves as the origin of the kinetochore microtubules, which interact with kinetochores. Kinetochores in turn are attached to the __________ that, during prophase, are associated with sister chromatid pairs.

(o)                    During what phase of mitosis does ribosome synthesis restart?

(p)                    What is the role of nonkinetochore microtubules in mitosis?

(q)                    What cytoskeleton component is associated with cytokinesis?

(r)                     Mechanisms that serve to inhibit cell division in healthy organisms (i.e., mechanisms of restraint on cell division) include a lack of immortality, a requirement for proper extracellular growth factors, and __________.

(s)                     Distinguish chromatin from chromosome.

(t)                     The S of S phase stands for what specific word and what important step of the cell cycle occurs during S phase?

(u)                    Metaphase ends when __________ and __________?

(v)                    What results when cytokinesis does not follow mitosis?

(w)                  What cytoskeleton component makes up spindle fibers?

(x)                    Once the cell cycle of a healthy cell proceeds to _________, the cell is committed to reproducing (i.e., progressing through mitosis).

(y)                    __________ is a complex of DNA and protein that, though present in large amounts in the nucleus of an interphase eukaryotic cell, is not visible through a light microscope.

(z)                    How many double helices of DNA does an individual sister chromatid (half of a sister chromatid pair) contain?

(aa)                 Name five things that are going on inside a cell during prometaphase that distinguishes this phase of mitosis from interphase as well as from the other phases of mitosis.

(bb)                During what phases of mitosis are nucleoli not at all present?

(cc)                 Name a protein or protein-containing complex (other than the various microtubules or the tubulin protein) that is directly associated with chromosomes during metaphase.

(dd)               Name four structures or complexes that make up the mitotic spindle in animals. I'm looking for answers other than cytoskeleton, chromosome, centromere, chromatid, or metaphase plate. Even excluding the above, by my count there are at least seven possible answers to this question.

(ee)                 During what phase of mitosis does cell lengthening begin to occur?

(ff)                  Chromatin is assembled predominantly from what two types of macromolecules?

(i)                     Carbohydrate

(ii)                   DNA

(iii)                 Lipid

(iv)                 Protein

(v)                   RNA

(gg)                During what phase of the cell cycle do sister chromatid pairs form?

(i)                     Cytokinesis

(ii)                   Gap 1 phase

(iii)                 Metaphase

(iv)                 Prophase

(v)                   S phase

(hh)                During mitosis through metaphase, sister chromatid pairs interact predominantly at their __________, a region of DNA and protein connecting these DNA double helices.

(i)                     Centriole

(ii)                   Centromere

(iii)                 Centrosome

(iv)                 Contronoma

(v)                   Disjunction

(ii)                    What is the last phase of the cell cycle during which nucleoli are still fully visible (not yet disappearing)?

(jj)                    During prometaphase, what must attach to sister chromatid pairs before such pairs may be visibly jerked about (as seen through a light microscope)?

(kk)                What, besides microtubules, does the mitotic spindle consist in animal cells during, for example, metaphase?

(ll)                    What purpose do the nonkinetochore microtubules serve during mitosis?

(mm)            At what stage of the cell cycle does a normal cell (i.e., noncancerous) become committed to reproducing?

(nn)                During what three phases of mitosis are nucleoli not present, not disappearing, and not reappearing?

(oo)                In a normal cell that is not dividing, what phase of the cell cycle is such a cell normally found in?

(i)                     Anaphase

(ii)                   G1

(iii)                 G2

(iv)                 M

(v)                   S

(pp)                Which is most associated with the type of cell division associated with most multicellular organisms (e.g., animals, which consist mostly of cells possessing only a single nucleus)?

(i)                     Binary fission

(ii)                   Meiosis

(iii)                 Meiosis followed by cytokinesis

(iv)                 Mitosis

(v)                   Mitosis followed by cytokinesis

(qq)                What is a cleavage furrow?

(rr)                   In what way are kinetochore microtubules functionally different from non-kinetochore microtubules?

(ss)                  Name three things that occur during telophase of mitosis.

(tt)                   What, in order of their occurrence, are the five phases of mitosis?

(uu)                During what phase of mitosis does the nuclear membrane disappear and centrosomes reach the poles of the dividing cell?

(vv)                Recapitulate mitosis as described in your text in Figure. Draw and describe (correctly!) all relevant events and detail. Avoid presenting extraneous detail not found in that figure, particularly if it does not occur during mitosis!!!

(ww)            What is chromatin?

(xx)                What does "G", "M", and "S" stand for when referring to M phase, S phase, and the various G phases of the cell cycle?

(yy)                Place in correct temporal order: Anaphase, Metaphase, Prophase, and Telophase.

(zz)                 During what phase of the cell cycle is the centrosome replicated?

(i)                     G0

(ii)                   G1

(iii)                 G2

(iv)                 M

(v)                   S

(aaa)             During what phase of mitosis do the mitotic spindles invade the region of the cell occupied by chromosomes?

(bbb)            The mitotic spindles directly interact with what centromere-associated protein complex? (neither chromosome nor centromere nor chromatid, sister or otherwise, are correct answers)

(ccc)             Cytoplasmic division is termed: __________.

(ddd)          True or False, chromatin is distinctly visible through a light microscope.

(eee)             True or False, following DNA replication, sister chromatids are visible, as distinct entities, through a light microscope.

(fff)               The cell cycle, at a gross level, consists of a combination of Interphase and ___________ phase.

(ggg)            Mitotic spindles begin to form during what phase of mitosis?

(hhh)            During what phase of mitosis do centrosomes reach the poles of the cell?

(iii)                  Draw an anaphase animal cell and describe what is going on. Assume 8 double helices present in a cell after S phase.

(jjj)                  Why are spindle fibers but not microtubules making up the normal cytoskeleton observable through a light microscope?

(kkk)            What is a cleavage furrow?

(49) Practice question answers [index]

(a)                    Chromatin is not visible through a light microscope while chromosome are.

(b)                    Binary fission is the mechanism employed by bacteria in their cell division.

(c)                    (i) (e), (ii) (d), (iii) (a), (iv) (b), (v) (c).

(d)                   iii, microfilaments.

(e)                    S (i.e., DNA synthesis)

(f)                     Drawing should include centrosomes at opposite poles, asters, spindle fibers, chromosomes (6 chromatids, 6 chromosomes), the chromosomes being dragged by their kinetochore, non-kinetochore microtubules.

(g)                    Assurance that a copy of each chromosome found in the parent cell is distributed to each daughter cell.

(h)                    A sister chromatid is the product of the replication of eucaryotic chromosomal DNA. It is characterized as being two more or less identical double helices which are attached at their centromeres

(i)                      Metaphase with six sister chromatid pairs lined up on the metaphase plate, and two of each type of chromosome present

(j)                      binary fission

(k)                    4

(l)                      making sure each daughter cell receives one (and only one) of each type of chromosomes (chromatin) found in the parent cell

(m)                  prometaphase

(n)                    centrioles, centromere

(o)                    telophase

(p)                    separating (pushing apart) the centrosomes

(q)                    actin/microfilaments

(r)                     lack of contact on all sides by other cells

(s)                     chromatin is not visible through a light microscope whereas a chromosome, by definition, is

(t)                     synthesis, DNA synthesis

(u)                    the chromosomes are separated at their centromeres and begin to be pulled to opposite ends of the dividing cell

(v)                    multinuclear cells develop

(w)                  microtubules

(x)                    S phase, DNA synthesis

(y)                    Chromatin

(z)                    One double helix of DNA per sister chromatid (two per sister chromatid pair)

(aa)                 "During prometaphase, [1] the nuclear envelope fragments. The [2] microtubules of the spindle can now invade the nucleus and [3] interact with the chromosomes, which [4] have become even more condensed. Bundles of microtubules extend from each pole toward the middle of the cell. [5] Each of the two chromatids of a chromosome now has a specialized structure called a kinetochore, located at the centromere region. Some of the [6] microtubules attach to the kinetochores. This interaction causes the [7] chromosomes to begin jerky movements. [8] Nonkinetochore microtubules interact with those from the opposite pole of the cell." p. 210, Campbell et al., 1999; see also "prometaphase" above

(bb)                During prometaphase, metaphase, and anaphase nucleoli are not present with a cell

(cc)                 Kinetochores

(dd)               Microtubules, tubulin, kinetochore microtubules, nonkinetochore microtubules, centrioles, centrosomes, spindle fibers, aster

(ee)                 Anaphase is the phase that I am looking for, but metaphase is also an acceptable answer (i.e., see photos on pp. 210-211 of your text)

(ff)                  (ii) DNA, (iv) Protein

(gg)                (v) S phase

(hh)                (ii) Centromere

(ii)                    Gap 1 of interphase

(jj)                    Kinetochore microtubules

(kk)                Centrosomes

(ll)                    Pushing centrosomes to opposite poles; increasing length of cell by pushing apart centrosomes; probably holding centrosomes in place while they drag chromosomes to opposite poles during prometaphase, metaphase, and, most dramatically, during anaphase

(mm)            S phase

(nn)                Prometaphase, metaphase, anaphase

(oo)                (ii) G1

(pp)                (v) Mitosis followed by cytokinesis

(qq)                A cleavage furrow is the actin-associated invagination of the cell membrane that arises during cytokinesis

(rr)                   Kinetochore microtubules are connected via kinetochores to the centromeres of chromosomes

(ss)                  Chromosomes stop being separated, nuclear membrane reforms, nucleoli reform, chromosomes de-condense back into chromatin

(tt)                   Prophase, Prometaphase, Metaphase, Anaphase, Telophase

(uu)                Prometaphase

(vv)                See Figure of your text.

(ww)            Chromatin is a complex of DNA and protein and/or chromatin is genomic DNA in eukaryotic cells that is not visible as individual chromosomal entities through a light microscope and/or prior to cell division (M phase) a eukaryotic cell's genome consists of chromatin

(xx)                Gap, Mitosis, Synthesis

(yy)                Prophase, Metaphase, Anaphase, Telophase

(zz)                 (iii) G2

(aaa)             Prometaphase

(bbb)            Kinetochores as well as centrosomes and/or asters (only one sufficient to answer correctly)

(ccc)             Cytokinesis

(ddd)          False

(eee)             False

(fff)               M

(ggg)            Prophase

(hhh)            Prometaphase

(iii)                  Note that the chromosomes now consist of individual sister chromatids (not pairs) and should pulled form their middle towards the poles of the cell

(jjj)                  Spindle fibers consist of bundles of microtubules

(kkk)            A cleavage furrow is the actin-driven invagination of the plasma membrane associated with cytokinesis

 

Chapter 12, Bio 113 questions:

 

(#) Besides division of cytoplasm, what is the "goal" of cell division?

 

A: equal partition of two more-or-less identical copies of genetic material between two daughter cells

 

(#) The complex of DNA and protein found in eukaryotic cells other than during M phase, which is not visible through a light microscope as discrete chromosomes we refer to as __________.

 

A: chromatin

 

(#) True or False, following S phase but prior to M phase, sister chromatids are not visible through a light microscope as distinct entities.

 

A: True

 

(#) What is a centromere?

 

A: A centromere is the region of a sister chromatid pair connecting sister chromatids

 

(##) Indicate what are the five phases of mitosis, in proper temporal order, and include three details about each phase that is unique to that phase. Note, for one of the phases (and only one) you may limit yourself to only one detail. To avoid ambiguity, by all means consider justifying your answers.

 

A: prophase (separation of centrosomes, chromatin begins condensing into chromosomes, spindle apparatus begins to form, nucleoli disappears, centromeres become visible), prometaphase (nuclear membrane disappears, mitotic spindle invades former nuclear region, chromosome fully condense from chromatin, centrosomes reach poles of cell, attachment of mitotic spindle to centromeres, visible jerking about of chromosomes), metaphase (sister chromatid pairs lined up in center of cell, metaphase plate, ), anaphase (sister chromatids separate, number of chromosomes doubles, movement of chromosomes towards poles of cell, pulling of chromosomes along kinetic ore microtubules towards poles of cell), telophase (chromosomes decondense back into chromatin, nuclear membrane reforms, nucleoli reappear).

 

(#) Which cytoskeleton component is most associated with cytokinesis in animal cells?

(i)                       Actin

(ii)                     Intermediate filaments

(iii)                    Keratin

(iv)                   Kinetochore microtubules

(v)                     Tubulin

 

A: (i) Actin