BIO 1140 Lecture Notes - Lecture 14: Apaf1, Nuclear Membrane, Tubulin

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Cell cycle Regulation
All cells were dividing at the same time and taking exactly the same time to do so. If cells are of
the same cell type, they have the same duration that takes them the same amount of time to
be able to do that.
In a womb the signals telling the cells what to do are there, so that the embryo can develop.
How do cells interpret the external and internal environment that they are in so that they know
its tie to diide ad get ead to divide?
Mitosis: Understand what’s going on.
Mitosis will represent just the last hour of a day if compared to a whole day of cell cycle.
The first growth phase (G1): before DNA replication, what needs to happen? Transcription,
translation and post translational modifications. Build all machinery needed to replicate DNA.
Cell needs to grow to make room for the duplicated DNA copy. Before going ahead and starting
DNA dupliatio, e eed to hek if eethig is alight. Thees a poit i G hee e ake
sure everything is ready for replication and that the cell has everything it needs to be able to
survive and thrive the two identical cells it will become once the cell cycle is complete, and it’s
called G0 (quiescent stage). Places cell in holding pattern, have opportunity to go and catch up
(not enough helicase available, not enough room, not enough nutrients).
Synthesis phase (S): DNA replicates and all other chromosomal proteins.
Growth phase 2 (g2): Also need energy so mitochondria are going over-time. More lipids to
have more membrane. All necessary organelles duplicated.
At the end of G2, one more checkpoint called (G2 / M checkpoint).
Mitosis: Need to organize all that DNA eause ou dot at diffeet piees of DNA i the
two cells, you want exactly the same pieces in both cells. Check point between metaphase and
anaphase, because everything is lined up and attached to spindle. This is called M-phase
checkpoint. Maybe not all chromatids are lined up with a spindle.
Soe ells puposefull dot diide ad stay at G0, they will not initiate apoptosis.
Question: While in the process of dividing, a cell is exposed to Colchicine (a drug that interferes
with spindle formation), at what stage will mitosis be arrested? Metaphase, cause of the M-
phase checkpoint, if all is not well > stay in metaphase.
Checkpoint are molecular switches. Tie the cell cycle to signal transduction: the cell requires
signals for growth for examples which are received using receptors and those signals include
growth factors. At each of those checkpoint, we are looking for different molecular
communication that will tell the cell that it can move forward. Need to find a way if what we
wanted to achieve before the checkpoint have actually been achieved.
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Document Summary

All cells were dividing at the same time and taking exactly the same time to do so. If cells are of the same cell type, they have the same duration that takes them the same amount of time to be able to do that. In a womb the signals telling the cells what to do are there, so that the embryo can develop. Mitosis will represent just the last hour of a day if compared to a whole day of cell cycle. Cell needs to grow to make room for the duplicated dna copy. Dna dupli(cid:272)atio(cid:374), (cid:449)e (cid:374)eed to (cid:272)he(cid:272)k if e(cid:448)e(cid:396)(cid:455)thi(cid:374)g is al(cid:396)ight. Places cell in holding pattern, have opportunity to go and catch up (not enough helicase available, not enough room, not enough nutrients). Synthesis phase (s): dna replicates and all other chromosomal proteins. Growth phase 2 (g2): also need energy so mitochondria are going over-time.

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