anaphase.html: 12_08AnaphaseKinetochor1.jpg
Inquiry:
During anaphase, do kinetochore microtubules shorten at their spindle pole ends or their kinetochore ends?
The microtubules of a cell in early anaphase were labeled with a fluorescent
dye that glows in the microscope (yellow).
EXPERIMENT
anaphase2.html: 12_08AnaphaseKinetochor2.jpg
EXPERIMENT
A Laser was used to mark the kinetochore mircotubles by eliminating the
fluorescnce
in a region between
one spindle pole and the chromosomes. As anaphase proceeded, researches monitored the changes
in the lengths of the microtubles on either side of the mark.
RESULTS
anaphase3.html: 12_08AnaphaseKinetochor3.jpg
RESULTS
As the chromosomes moved toward the poles, the microtubule segments on the
kinetochore side of the laser mark shortened, while those on the spindle pole side stayed the same length.
CONCLUSION
anaphase4.html: 12_08AnaphaseKinetochor4.jpg
CONCLUSION
During anaphase, the spindle fibers shorten by depolymerizing and losing tubulin
subunits at the kinetochore. A motor protein then moves the kinetochore
and its attached chromosome toward the spindle pole.
binary_fission.html: 12_11BinaryFission.jpg
Bacterial cell division (binary fission)
Chromosome replication begins at the origin of replication where replication begins.
One copy of the origin moves toward the other end of the cell; DNA is deuplicated.
When one copy of the origin reaches the other end of the cell, replication is complete.
The plasma membrane grows inward, and new cell wall is deposited.
Two daughter cells result.
cell_division.html: 12_02CellDivFunctions.jpg
Reproduction. An amoeba, a single-celled eukaryote, is dividing into two cells. Each new cell will be an individual organism. | Growth and development. This micrograph shows a sand dollar embryo shortly after the fertilized egg divided, forming two cells. | Tissue renewal. These dividing bone marrow cells (arrow) will give rise to new blood cells. |
cells.html: ../ch06/06_02CellSizeRange.jpg
chromosome.html: 12_04ChromosomeDuplicat.jpg
To prepare for cell division, DNA is replicated and
each duplicated chromosome has 2 sister chromatids, attached by a centromere.
The chromatids separate during cell division.
chromosomes.html: 12_03EukChromosomes_LP.jpg
Eukaryotic chromosomes condense and become visible during cell diviison.
cycle.html: 12_05CellCycle_L.jpg
The cell cycle.
The mitotic (M)
phase alternates with interphase, which is composed of 2 growth phases
(G1 and G2)
and a S (DNA synthesis) phase.
In the M phase, mitosis divides the nucleus,
and cytokinesis divides the cytoplasm, producing 2 daughter cells.
cytokinesisA.html: 12_09CytokinesisA.jpg
Cytokinesis in animal cells.
In animal cells, a cleavage furrow forms, pinching the plasma membrane.
Then a contractile ring of microfilaments splits the cell.
cytokinesisP.html: 12_09CytokinesisP.jpg
Cytokinesis in plant cells.
In plant cells, vesicles containing cell wall material fuse to form a cell plate.
The cell plate grows and fuses with the existing cell wall,
dividing the cell in two.
division.html: 12_01ChromosomesCellDiv_UP.jpg
DNA in nondividing eukaryotic cells (far left and far right)
is complexed with proteins in dispersed fibers called chromatin.
The chromatin condenses into visible chromosomes during cell division in a process called mitosis.
mitosis-anaphase.html: 12_mitosis-anaphase.jpg
Anaphase.
The 2 sister chromatids part, moving toward opposite ends of the cell,
Each chromatid is now a full-fledged chromosome.
The kinetochore microtubules shorten, while
nonkinetochore microtubules lengthen, stretching the cell.
mitosis-g2.html: 12_mitosis-g2.jpg
G2 of Interphase.
mitosis-metaphase.html: 12_mitosis-metaphase.jpg
Metaphase.
The chromosomes convene on the metaphase (equatorial) plate.
For each chromosome, the kinetochores of the sister chromatids are attached to kinetochore microtubules coming
from opposite poles.
mitosis-prometaphase.html: 12_mitosis-prometaphase.jpg
Prometaphase.
The nuclear envelope fragments.
Each of the 2 chromatids has a kinetochore,
which attach the chromatid to the spindle microtubules at the centromere.
mitosis-prophase.html: 12_mitosis-prophase.jpg
Prophase.
The chromatin fibers condense into discrete chromosomes observable with a light microscope.
The nucleoli disappear.
The mitotic spindle, composed of microtubules, begins to form.
mitosis-telophase.html: 12_mitosis-telophase.jpg
Telophase.
Two daughter nuclei begin to form in the cell.
Nuclear envelopes reform.
The chromosomes become less condensed.
Mitosis, the division of one nucleus into two genetically identical nuclei, is now complete.
mitosisA.html: 12_06aMitoticDivision_CL.jpg
Stages of mitosis.
From the
G2
subphase of Interphase, the dividing cell proceeds through
prophase
to
prometaphase.
continue
mitosisB.html: 12_06bMitoticDivision_CL.jpg
Stages of mitosis continued. A dividing cell continues through
metaphase,
anaphase,
and finally
telophase
and cytokinesis.