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In
interphase, the DNA is neatly contained within the
nucleus and is not condensed into chromosomes. Microtubules
are radially arrayed from the center of the cell and if
this cell was not fixed and dead the microtubules would
be highly dynamic, shrinking and growing from their ends.
When a cell is ready to divide it will replicate both its
DNA and cellular contents and then split into two in the
process known as mitosis described below. The images here
come from Xenopus XL-177 cells, and were taken by
Claire Walczak.
Tubulin is shown in green,
DNA in blue.
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metaphase, the nucleus has broken down, DNA has condensed
into chromosomes and through a fair amount of pulling and
pushing by microtubules that have formed the mitotic spindle,
the chormosomes are aligned in the center of the cell. Through
attachments at kinetochores the microtubules are linked to
chromosomes. |
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Connections
that hold the metaphase chromosomes together break in anaphase,
and the chromosomes move to opposite spindle poles. Through
a number of mechanisms that include chewing up microtubules
and reeling in microtubules the chromosomes are segregated
to seperate poles; a full complement of chromosomes to each.
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Telophase, the DNA is safely segregated and the cell
divides into two during cytokinesis. At the middle of the
cell actin, septins, mysosins, microtubules, and other proteins
gather as the cell setups up a ring of proteins that will
constrict, sealing off the bridge between what was once one
cell. |
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In
vitro spindle assembly
This
image shows the localization of microtubules and DNA in
a mitotic spindle assembled in vitro in a cytoplasmic
extract from Xenopus laevis eggs.
Tubulin is shown in red,
DNA in blue.
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People
and Projects
Aaron Groen studies the
assembly and dynamics of the spindle pole.
Paul
Chang is looking for the matrix
Zoltan Maliga is characterizing
monastrol, an inhibitor of the mitotic kinesin Eg5.
Puck Ohi and Adrian
Salic are characterizing novel spindle-associated factors.
Zach Perlman is developing
new techniques for analyzing spindle dynamics.
Kendra Burbank is modeling
spindle dynamics.
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