Cell cycle Regulation\ Flashcards
(49 cards)
Cell fusion experiment procedure
Cancer cells were fused from different stages of the cell cycle to determine if the nucleus’ would influence each other
Cell fusion experiment results
The concluded that the cytoplasmic molecules caused G1– S and G2–M
Experiment determining how cell fusion worked
Hartwell used baking yeast and grew yeast mutants at a normal temperature and then heated them up. He identified where the mutants got stuck. Compared their DNA with DNA from healthy cells
Cell phase experiment results
Some problems were DNA replication, mostly they were cell cycle regulation problems
Paul Nurse’s experiment
Similar to Hartwell but he used fission cells instead of budding cells. He discovered CDC2
CDC2 discovery
Encodes a protein needed for G2–M phase. Protein Kinase (inactive or active proteins). All cells have this gene suggesting that it occurred early in the evolutionary pathway
Cyclins
Proteins that control the cell cycle
3 checkpoints in the cell cycle
Prevent critical phases form starting to early, or with improper cells. G1/s, G2/M, mitotic spindle checkpoint
G1/S checkpoints
Decides if a cell will start duplicating its DNA.
G1/S stops if…
DNA is damaged from radiation or chemicals. If extracellular signals (hormones, growth factors) are not present
G2/M checkpoint
Decides if a cell will enter mitosis
G2/M stops if
DNA was not properly replicated or is damaged
Mitotic spindle checkpoint
Checks if spindles are properly attached and that chromosomes are properly lined up on the metaphase plate. Essential for producing identical cells
Cell regulation involves
Cyclins and cyclin dependent kinases
Cdks
Protein kinase (phosphorylates and regulates target protein activity, cyclin dependent, and the concentration remains constant which cyclin concentration changes
Cyclin dependent
Is only active when cyclin is present and bonded to it
Each Cdks
Is active at a different time and regulates cell activities
Cyclin cdks complex regulation
Integrated into each checkpoint
G1/S Cyclin cdks complex regulation
G1/s cyclin binds to cdk2 at the end of G1 causing the cell to commit to DNA replication
G2/M Cyclin cdks complex regulation
S cyclin binds to the cdks2 in the S phase, DNA replication is initiated and the cell progresses through S phase
Mitotic spindleCyclin cdks complex regulation
My cyclin binds to cdks1 in G2 causing G2 to become mitosis.
M phase promoting factor
MPF, know as the M cyclin-cdk1 complex. Activates APC at the end of metaphase (if the spindles are properly attached)
Anaphase promoting complex
Degreades anaphase inhibitor allowing anaphase to occur
In late anaphase it degrades M cyclin which deactivates cdk1
Deactivation of Cdk1 leads to
chromosomes to elongate, nuclear envelope to form, and the cytoplasm to divide
