Cell Cycle Lecture - Pfeffer Flashcards
The cell cycle is controlled by a complex network of what?
Regulatory proteins
The eukaryotic cell is divided into how many phases?
4 active ones
What halts the cell cycle in unfavorable conditions?
Checkpoints, highly conserved
Control is a series of what 2 counterbalances?
Synthesis and Degradation
Phosphorylations and dephosphorylation
What occurs during the M phase?
Mitosis and Cytokinesis
What does G1/G2 (gaps) allow the cell to do?
Monitor signals and prepare for the next phase
What is the basis of control for the cell cycle?
Cyclically activated protein kinases
What are some substances that disrupt microtubule function arresting the cell in M phase?
Colchicine, vinblastine, vincristine, taxol
Agents such as cytochalasin arrest in late M phase, why?
They disrupt microfilament structure and cytokinesis cannot occur
What phase to agents that inhibit DNA synthesis arrest the cell cycle in?
S phase
What cell phase occurs over the most variable amount of time?
G1 (6-12 hours)
What type of cells are not known to replicate DNA? Give a few examples.
Permanent cells; neurons, fat cells
What kind of cells have the potential to divide but await a signal? Give a few examples
Stable cells like hepatocytes and fibroblasts
What kind of cells continue to divide throughout life? Give some examples.
Labile cells; bone marrow cells, epithelia
What does the G2/M “Checkpoint” check for?
Is all DNA replicated, is cell big enough.
What does the G1/S “checkpoint” check for?
Is cell big enough, is environment favorable, is DNA damaged.
What were the conclusions of Ras and Johnson nuclear fusion experiments? (4)
1) S phase nucleus releases something that drives G1 nucleus into S
2) G2 nucleus is resistant to S phase promoting factor
3) G1 and G2 do not influence each other
4) Mitotic nuclei release mitosis-promoting factor that affects all interphase nuclei
G1 phase controls what aspect of proliferation in most mammalian cells? What happens if G1 does not progress to S?
Rate is controlled; If not ready it goes into a Sleep (G0) cycle with an RNA and protein synthesis step-down or even apoptosis when under stress
Initiation of DNA synthesis in S phase occurs first with what? and then with? What also happens during S phase?
Euchromatin then Heterochromatin; Synthesis of key proteins: histones, enzymes, etc.
What happens during G2?
Synthesis of proteins required for mitosis
What phase is the best characterized that also has almost no RNA synthesis?
M phase
What is the Hayflick number and how is it related to age and capacity?
Proliferation number; inversely related to age and capacity
True or False. Cells have a limited lifespan.
True
What is progeria?
Premature aging
