Lecture 20 - Cell Cycle Flashcards
What are the two general phases of the cell cycle?
Interphase and M Phase
Interphase is comprised of
G1, S, G2
In what phase is the cell not dividing?
Interphase
In what phase is the cell dividing?
M Phase
G1 Phase of Interphase
The first phase of cell growth and organelle duplication
G0 Phase
When a cell exits the cell cycle either permanently or for long periods of time; the cell stops expressing genes required for the cell cycle.
Examples of cells in G0
nerve, muscle, cardiac cells
S Phase
DNA Replication
How many chromosomes are replicated during S Phase?
46
What copies DNA during S Phase?
DNA Polymerase
What holds two strands of DNA together?
hydrogen bonds
What holds chromosomes together?
Cohesions
Steps to DNA Replicaiton
- Unzipping
- DNA Polymerase makes a copy using base pairing rules
- Sugar phosphate backbone formed connecting nucleotides in the two new strands
G2 Phase of Interphase
The second phase of cell growth and organelle duplication
M Phase
Mitosis and Cytokinesis
Mitosis Steps
Prophase, Prometaphase, Metaphase, Anaphase, Telophase
Mitosis
Nuclear Division
Prophase
The replicated chromosomes condense. The centrosomes begin to move to opposite sides of the nucleus and the mitotic spindles begin to form.
Prometaphase
nuclear envelope breaks down, spindle fibers contact at the kinetochore located at centromeres
Kinetochore
protein complexes which assemble on the condensed chromosomes
Metaphase
Mitotic spindle gathers all the chromosomes to the center of the spindle
Anaphase
The two sister chromatids in each replicated chromosome synchronously split apart. The spindle draws them to opposite poles of the cell.
Specifically, when does anaphase begin?
When the cohesions are cleaved
Steps of Coheasins Cleavage
- APC phosphorylated by MCdk
- Phosphorylated APC activated when Cdc20 binds
- Activated APC ubiquinates securin
- Securin is degraded and separase is activated
- Separase cleave cohesins
Telophase
Nuclear envelope reassembles around each of the two sets of separated chromosomes to form two nuclei. Nucleus expands and chromosomes condense to interphase state. Contractile ring assembles.
Cytokinesis
cytoplasmic division, including all organelles, by the contractile ring
When does cytokinesis begin and end?
Begins in anaphase and ends at the end of telophase
