cell cycle Flashcards
what are the different cell cycle phases ?
G1 growth phase
S synthesis of DNA
G2 growth
M mitosis
what are checkpoints in the cell cylce regulated by ?
cyclins
cyclin dependent kinases
what is thee shortest phase of the cycle ?
mitosis
what are the phases of mitosis ?
prophase
prometaphase
metaphase
anaphase
telophase
what is the differences between cyclins and cyclin CDK complexes ?
CDKS alone are not active
when bound to cyclins and become a complex they become active
what are the different cell types inn association to the cell cycle ?
labile never go to g0
permanent remain in g0
stable enter g0 when stimulated
when does g0 happen ?
when there are no mitogens
what are examples of each cell type ?
permanent - neurones skeletal cardiac muscles RBC
stable - hepatocytes, lymphocytes
labile - bone marrow, gut epithelium skin and hair
when doo the checkpoints happen throughout the cell cycle ?
from g1 to s
from g2 to m
what is the rrole of mitogens ?
they activate CDK which in turn allows for the release off cyclins
what is the checkpoint between the G1 to s phase ?
through thee releasee of the E2F protein
which iis usually inactive as it is bound to Rb
thee cyclin CDK complex allows for the phosphorylation of the retinoblastoma protein and releases thee E2F which allows for the continuation of the cell cycle
what is E2F ?
a transcription factor which is released to allow thee continuation of the cell cycle in thee G1 to S phase
how can cells b arrested in the G1 to S checkpoint ?
by one of two pathways
either the ATM pathway or the ATR pathway
ATM - ataxia telegenctasia , where there is a double stranded breaks
ATR - single stranded breaks
both these pathways lead to phosphorylation of p53
where does p53 come in ?
after DNA damage by one of the pathways
p53 is phosphorylated and becomes stable
which leads to the transcription of p21
what does p21 do ?
when transcribed it inhibits the cyclin -CDK
so cell cycle is arrested
