Enabling Replicative Immortality Flashcards
Wha would happen if normal cells didn’t divide a certain number of times?
Tissues would lose their structures and would also lose their abilities/functions
What happens if cells continue to accumulate mutations?
Impacts control mechanisms which maintain proliferation and apoptosis.
Why are fibroblasts used in labs?
They are robust and do not require special equipment
Describe the growth curve of the population of normal fibroblasts
- cells double every 2 or 3 days, exponential
- until they are 170-200 days old, where they reach senescence and stop dividing.
What dye can detect senescent cells?
Beta galactose
What are the differences in morphology between normal tissue and tissue with cells reaching senescence?
Normal: good shaped cells with discrete nucleus, well ordered in monolayer.
Senescent: nucleus disappeared, disordered structure, cells filled with b-galactose.
Why is embryonic tissue used in labs?
Younger cells divide more efficiently/ more often than older cells.
What phase of the cell cycle is senescence?
G0.
What is senescence?
Cells in G0 phase (left active cell cycle)
Stable karyotype, metabolically active, normal respiration, just cannot divide
Why can cancer cells avoid senescence?
Normally, once a cell goes into G0, it is almost impossible to return to metaphase.
Cancer cells lose the inhibition to go back into metaphase, so they can return to the cell cycle and continue proliferating
How can we partially achieve senescence in the lab?
RB and P53 inhibition
What happens if both P53 AND RB are inhibited?
Cells are able to grow exponentially forever with no plateau (unlike normal growth curve)
What is replicative crisis?
When cells are forced into apoptosis
What is replicative crisis dependent on?
Telomeres: DNA on end of chromosomes
What does the loss of telomeres result in?
Apoptosis
