slide set 16 Flashcards
cell divisions in your body
bone marrow stem cells: 1,000,000/min
cell theory
all cells are made up of other cells
cell cycle basics
Cell must
- grow
- replicate its genome
- centrosomes must be segregated to opposite ends of the still-growing cell
- cytoplasm is cleaved in half
- 2 daughter cells, identical in size to original cell
S+M phase
S Phase: chromosomes are duplicated (entire genome is duplicated)
M Phase: Mitosis and Cytokinesis
4 cell cycle stages
Interphase
- M phase
- G1 phase
- S phase
- G2 phase
G = gap
mitosis is easy to see through a microscope, but what about the other stages
- we can detect S phase
How can we identify S phase?
- detect cells that are replicating their DNA
- 2 options
- Detect S-phase by DNA replication and incorporation of a modified base
* detect BrdU with an antibody
* treat cells with BrdU for a certain amount of time- if it is dividing, it’ll include BrdU
- if it isn’t, the cell won’t take in any bases floating around
* bind antibody to BrdU, cell that fluoresces has been in S phase
- Detect S-phase by DNA replication and incorporation of a modified base
- Measure relative DNA content per cell by flow cytometry = fluorescent label on DNA is detected
How can we identify S phase (part 2)?
harvest cells
isolate cells
stain cells
- Measure relative DNA content per cell by flow cytometry = fluorescent label on DNA is detected
fluorescent dye shows us how much DNA is there
height of peak = # of DNA in cells
peaks change bc cells divide at random times
cell cycle controllers
- proteins control when each process occurs
- These proteins integrate signals and can slow or stop the cell cycle if conditions are unfavorable or if errors have occurred
CDK aka
cyclin-dependent kinase
key enzyme family
Cdk’s
require a cyclin partner before they are active as a kinase
major Cdk’s and their cyclin partners
each active Cdk recognizes and phosphorylates specific target proteins that ultimately drive a cell cycle phase
focus on M-Cdk (mitotic Cdk)
Cdk enzyme activity over course of cell cycle stages
Cdk enzyme activity rises abruptly and declines abruptly at cell cycle stages
what happens if we add an inhibitor that blocks cells from getting to S phase
we’d have one really large peak in G1
Rise in Cdk activity is based on…
synthesis and degradation of cyclins
M phase questions
Are all chromosomes attached to the spindle?
(If not, we may get uneven daughter cells)
Metaphase to Anaphase transition
G1
restriction point: point of no return, after cell crosses that point cell is committed to rest of cell cycle and dividing
Is environment favorable?
enter cell cycle! proceed to S phase!
G2 questions
Is all DNA replicated?
Is environment favorable?
G2/M transition!