cell division Flashcards
(44 cards)
why is cell division required
growth and reproduction and repair of tissues in multicellular organisms
cell division 4 events
cell division signals
dna replication
dna segregation
cytokineses
cell division signals
1(+) signals are required to initiate cell division
dna replication
each of the 2 new cells will have a full complement of genetic information (starts at ori and ends at ter)
dna segregation
replicated DNA must be distributed appropriately to the 2 daughter cells (moved towards opposite ends)
cytokinesis
cytoplasm must divide to form the 2 new cells (starts immediately after end of chromosome replication)
how do prokaryotic cells divide
binary fission
how do eukaryotic cells divide
mitosis followed by cytokinesis
in cytokinesis, dna segregation happens during
mitosis
eukaryotic cell passes through which phases before division?
cell cycle (G1, S, G2 and M)
m = mitosis and cytokinesis
other three = interphase
G1
each chromosome (unduplicated molecule)
S phase
DNA replication occurs
- each chromosome = two sister chromatids
G2 phase
preparation of mitosis
in a cell cycle of 24 hours, how long does each phase last
G1 = 11
S = 8
G2 = 4
M = 1
what are the 3 main transition points
S phase, Mitosis entry, chromosome segregation
what controls transition between stages
specific internal signals
what controls G1 to S transition
cyclin-dependent kinase (CDK)
what is G1 to S transition called
restriction point (R point)
what does CDK activation requires
cyclin binding
the accumulation of cyclins helps regulate
activity of CDKs
cyclin concentrations are regulated by
protein synthesis and degradation
checkpoint triggers of each phase?
g1 = dna damage
s = incomplete replication or dna damage
g2 = dna damage
m = chromosome unattached to spindle
dna damage in g1 activates
p53 (transcription regulator)
p53 activates the transcription of
p21 (CDK inhibitor protein)
