Mitosis and the Cell Cycle LO Flashcards
what is the point of the restriction point (R)?
cell must be large enough to move to the next stage (S)
What happens once the cell passes the R phase?
cell is committed to cell cycle
what is the main goal of somatic cell cycle?
ensure exact duplication of genome in S phase followed by exact division of genome in M phase to produce identical daughter cells
how is regulation accomplished throughout the cell cycle?
variation in cyclin concentrations regulate activation of CDKs which in turn regulate formation of pre-replication complex (pre-RC)
what is the level of CDK at start of G1?
low to allow formation of pre-replication complex (pre-RC)
what is level of CDK activity at S?
high, allows activation of pre-RC
what does high CDK activity do to pre-RC formation?
blocks it
what is the level of CDK in M phase?
high, to allow for cell replication
what does chromosome re-replication complexes in S phase or mis-segregation during mitosis produce?
cancer and birth defects
what is aneuploidy?
incorrect number of chromosomes in a cell
what is the difference between mitosis and meiosis in regards to the numbers and types of cells created?
mitosis = 2 identical diploid cells meiosis = 4 non-identical haploid cells
what are the 6 phases of mitosis?
- interphase
- prophase
- metaphase
- anaphase
- telophase
- cytokinesis
what occurs during interphase?
cell growth
what occurs during prophase?
chromatin condenses
what occurs during metaphase?
chromosome line up at metaphase plate
what occurs during anaphase
sister chromatids separate and are pulled to opposite ends of cell
what occurs during telophase?
new nuclear membrane surrounds each sister chromatid
what occurs during cytokinesis?
cell divides into 2 diploid cells
what occurs in meiotic prophase?
chromosomes replicate resulting in 2 homologous chromosomes
when does crossing over take place?
during meiotic prophase when sister chromatids are formed
what occurs during meiosis I?
homologs are separated into 2 cells (reductional division)
what occurs during meiosis II?
each pair of sister chromatids separated into different cells resulting in 4 haploid cells (equational division)
what types of cells are stuck in the R point of the cell cycle?
neurons, and then continue to grow without entering the cell cycle
what is a CDK?
cyclin-dependent kinase
what are CDK’s activated by?
cyclins
what are CDK’s inhibited by?
Cip/Kip or Ink4 classes of CDK inhibitors
what are 4 common cell cycle regulators that are commonly associated with cancer?
- retinoblastoma protein (rb)
- p21 or p16
- mitogens
- CDK’s and cyclins
what is the function of retinoblastoma protein (Rb) and what is result of mutation?
cell cycle inhibitor, loss of Rb leads to tumors
what is the function of p21 or p16?
Cip.Kip and Ink4 CDK inhibitors respectively (loss of them results in cancer)
what is function of mitogens?
growth factor
what happens if there is an increase of mitogens?
increased cell proliferation possibly leading to cancer
what is function of CDK and cyclins?
cell cycle activators
what happens when there are increased levels of CDK and cyclins?
increased cell proliferation
what is the cell cycle checkpoint in G1?
monitors cell size and damage to cell
what is cell check point in G2?
checks for damage of new DNA
what is the cell checkpoint during mitosis?
spindle formation
what is the mechanism of a cell cycle checkpoint?
- damage detected by sensor
- transducers relay information to effectors through a signaling cascade
- effectors arrest cell cycle until damage is remedied
where is information immediately relayed to when cell damage is found?
ATM and ATR
what type of cell damage is ATM specific to?
double strand breaks
what type of cell damage is ATR specific to?
non-specific
what is the pathway in cell cycle arrest involving BRCA2?
ATM and ATR relay information to BRCA2 which activates Chk1 or Chk2.
what does the BRCA2 pathway ultimately lead to?
cell cycle arrest, production of repair enzymes, or activation of p53
what molecule is p53 activated by in damaged cells?
Chk2
what is the pathway of cell cycle arrest that does not involve BRCA2?
direct activation of p53 which activates CDK inhibitor p21 leading to cell cycle arrest
what happens in S phase?
chromosome synthesis (replication) occurs
what occurs in M phase?
chromosome segregation
what happens in G1 and G2 phases?
gap phases before S and M phase. Cell regulation occurs in these phases. G1 contains restriction point (R)
how is retinoblastoma protein (Rb) deactivated?
phosphorylation by CDK phosphorylation
