|As cells divide, towards the end of the end of
cell division, it appears that each new daughter
cell gets longer. Is this the result of the
pinching in that occurs during cytokinesis, or
are the cells getting longer. Of the two
options, which one is primarily responsible for
this effect?How do cells sort their organelles
during cell division? Is it the luck of the
draw, or a genetically programmed set of
instructions at work?
Those are some good questions. Let me see if I
can help a little bit.
First off, during cytokinesis the cells do
elongate. I am uncertain as to why that
happens, nor could I find any references to
address that issue. However, one may argue that
elongation of the daughter cells facilitates the
separation of the chromosome and organelles.
Because microtubules are laid down "end to end" so
to speak, their formation results in long tracts
upon which are used to draw the cellular
constituents apart. That's my guess... As you may
have guessed, this story is complicated. Some of
them randomly sort out (e.g. mitochondria). Note
however, that not all of them seem to sort out.
Here's the best summary that I could find:
The nuclear envelope: There is still
controversy over whether the nuclear envelope
pinches off in prophase to form many small
vesicles, which reassemble later during telophase,
or whether nuclear envelope proteins, freed from
some constraint, laterally diffuse out into the
ER, which itself vesiculates. ER and Golgi
cisternae vesiculate in most cells.
In telophase, vesicles surround the
decondensing chromosomes, perhaps mediated by
interaction of lamin B with chromatin. The
vesicles fuse to form the nuclear envelope, as the
lamina reassembles. Once nuclear pore complexes
reassemble, uptake of proteins with nuclear
localization signals occurs.
Movement of ER and Golgi membranes along
microtubules, mediated by kinesins and dyneins,
may re-establish organellar locations in the
interphase cell (Golgi near the centrosome, and ER
toward the cell periphery).
Many processes in mitosis are regulated by
phosphorylation of proteins at the onset of
mitosis, and dephosphorylation of proteins in
anaphase (to be discussed further).
This info was taken from a web page of an
acquaintance of mine. The address is:
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