Cell Cycle Flashcards
two main stages of the cell cycle
mitotic and interphase
mitotic phase consists of
mitosis and cytokinesis
cell growth and copying chromosomes
interphase
3 parts of interphase
s, g2,and g1
DNA synthesis
s phase
period between s and m
g2
period between m and s
g1
5 phases of the mitosis
prophase prometaphase metaphase anaphase telophase and cytokinesis
the cell increases in size, the DNA of the chromosomes is replicated and the centrosome is duplicated
interphase
the duplicated chromosomes condense.
outside the nucleus the mitotic spindle assembles between the two centrosomes which have begun to move apart
prophase
breakdown of nuclear envelope, can now attach to spindle microtubules via their kinetochores and undergo active movement
prometaphase
the chromosomes are aligned at the equator of the spindle, midway between the spindle poles.
the kinetochore microtubules on each sister chromatid attach to opposite poles of the spindle
metaphase
the sister chromatids synchronously separate and are pulled slowly toward the spindle pole to which they are attached. he kinetochore microtubules get shorter and the spindle poles move apart
anaphase
the two sets of chromosomes arrive at the poles of the spindle. a new nuclear envelope reassembles around each set, completing the formation of two nuclei and marketing the end of mitosis
telophase
the cytoplasm divided in two by a contractile ring of actin and myosin filaments, which pinches the cell into two daughters each with one nucleus
cytokinesis
is all DNA replicated? is all DNA damage repaired?
checks for: cell size and dna damage
G2 checkpoint
are all chromosomes properly attached to the mitotic spindle
checks for: chromsome attachement to spindle
M checkpoint
is environment favorable?
checks for: cell size, nutrients, growth factors, dna damage
G1 checkpoint
which check point is the most important
G1
If the cell does not receive the go-ahead signal from the g1 phase, it will exit the cycle, switching into a non-dividing state called
g0 phase (senescence)
kinetochores not attached to spindle microtubules send a molecular signal that delays anaphase
internal signal
growth factors —- proteins released by certain cells that stimulate other cells to divide
external signals
cyclin- cdk complex: G1-Cdk
Cyclin?
Cdk partner?
Cyclin D
Cdk 4 and 6
cyclin- cdk complex: G1/S-Cdk
Cyclin?
Cdk partner?
Cyclin E
Cdk 2
cyclin- cdk complex: S-Cdk
Cyclin?
Cdk partner?
Cyclin A
Cdk 2
cyclin- cdk complex: M-Cdk
Cyclin?
Cdk partner?
Cyclin B
Cdk 1
three d cyclins in mammals
d1 d2 d3
Transcription
Proteolysis
Inhibitory phosphorylation
Binding of CDK inhibitors
regulations of cyclins
cyclins or cdk’s are degraded
cyclins
Ubiquitylation of cyclin by APC results in
degradation
The cell cycle can pause through the action of a CDK inhibitor
p27
p21
p57 (all for g1/s, g2, m)
g1 - 15, 16, 18, 19
DNA damage will result in exit from the cell cycle and arrest in
G1
three major categories of extracellular signals
mitogens
growth factors
survival factors
stimulate cell division (entry & progression through the cell cycle)
mitogens
stimulate cell growth (increase in cell size and mass) by promoting the synthesis of proteins and other macromolecules
growth factors
promote cell survival by suppressing programmed cell death
survival factors
- act by turning on signaling pathways that stimulate the synthesis of G1 cyclins
- inhibit the Rb protein
mitogens
in normal cells pRB is a
tumor supressor
Increase Synthesis and Decrease Degradation of Macromolecules, and results in increased cell size and mass
growth factors
a pro-survival protein
Bcl-2
Survival Factors Suppress Apoptosis by Regulating (oncogene)
bcl-2
which crowded cells stop dividing
external signal
in which they must be attached to a substratum in order to divide
anchorage dependence
which type of cells exhibit neither density-dependent inhibition nor anchorage dependence
cancer cells
proteolysis regulates what two cycles
s and m
inhibitory phosphates are removed to activate the
M-cyclin CDK complex
