Cell Cycle Flashcards
_ control transitions between phases of cell cycle. This process is regulated by _ and _ suppressors.
check points
cyclins dependent kinases and tumor suppressors
_ phase the shortest phas eof the cell cycle includes mitosis and cytokinesis
M
mitosis is broken down into?
Prophase, prometaphase, metphase, anaphase, and telomerase
_ is of variable duration
G1
cyclin-depedent kinaases are _ expressed but inactive when not bound to _
constituitively
cyclin
cyclins are ?
phase specific regulatory proteins that CDKs
cyline stimulate CDKs when
when they are stimulated by growth factors
the cyclin-cdk comples can do what
phosphorylate other proteins to aid in cell cycle progression
mutations in tumor suppressor genes can result in
unrestrained cell division (Li Fraumeni syndrome)
growth factos bind _ _ _ to transition the cell from G1 to S phase
tyrosine kinase receptors
what is a permenant cell type and what are some examples
these are cells that remain in G0 and regenerate from stem cells
example: neurons, skeletal muscle, cardiac muscle, RBCs
what are stable cell and give examples
stable cells are those that enter G1 from G0 when stimulated
example: hepatocytes, lymphocytes, PCT, periosteal cells
what are labile cells and give examples
cells that never go into G0 and divide rapidly and have a short G1
they are most affected by chemotherapy
examples: bone marrow, gut epithelium, skin, hair, germ cells
what happens in prophase
chromosomes condense and spindle fibers form (made up of microtubules)
what is prometaphase
chromosomes start to organize on mitotic spindle
metaphase
chromosomes line up at metaphase plate
anaphase
chromosomes seperate to opposite ends of the cell
telophase
spindle breaks and and cell divides
G1-S phase checkpoint is where the cell commits to growing: all checkpoints depend on?
CDKs
(cyclin depended kinases)
cyclin- regulatory proteins
subtypes of cyclins
A-D
levels fluctuate through cell cycle phases
during G1 phase CDK activity is _
_ activate CDK and entry into the S phase
suppressed
mitogens
how do mitogens activate CDks
they interact with cell surface receptors, activate intracellular pathways and increase G1 cyclin levels resulting in an increase in CDK activity
cyclin CDK complexes activate _ proteins
E2F
these are transcription factors that bind to DNA promoter regions and activate genes for S phase
E2F is normally inhibited by?
Rb (retinoblastoma protein) when the cyclin-Cdk complexes phosphorylate E2F the inhbition by RB is lost
Rb is a tumor suppressor
in the G1- S checkpoint _ damage allows for arrest in cell division, allowing for repoair and preventing the development of mutatant cells/cancer
damage
DNA damage initiates signaling pathways
DNA damage in the G1 phase causes cells to enter what pathways?
ATM or ATR
what is the ATM pathway
this is a pathway for double stranded DNA breaks
ATM= ataxia telangiectasia mutated
***ATM gene mutated leads to ataxia telangctasia
what is the ATR pathway
pathway for single stranded DNA breaks
ATM/ATR systems sensing DNA damage has a major target on?
what happens?
P53
P53 become phosphorylated, and stable, it induces P21 transcription. P21 will bind to CDK and inhibit progression through the cell cycle
both P53 and P21 are tumor suppressors
retinoblastoma mutation
RB1 gene which codes for the Rb protein
this allows E2F to allow progression from G1-S in an unregulated fashion
eye malignacy in children
what is Li-fraumeni syndrome
SBLA cancer syndrome
sarcomas, breast, leukemia, adrenal gland cancers at a young age
mutation in TP53 gene and not enough P53 which will allow for damaged DNA to accumulate and cause cancer.
