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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Course-external links are
in brackets Click [index] to access site index Click here to
access text’s website Vocabulary
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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]