Unit 7 Flashcards
G1 phase
Major period of cell growth where duplication of organelles and volume of cytoplasm is increased
After G1 phase cells can do 2 things
Enter s phase, or entered g0
S phase
DNA replication occurs, s cyclin and cdks are active
G2 phase
Cell size doubles in prep for mitosis and s cyclin and cdks are active
G2 /m checkpoint
Commitment to divide that is managed by m cdks
Fate of m cdk and m cyclins during mitosis
Active during first half, and the targeted for destruction during anaphase by the anaphase promoting complex (apc)
G0
Referred to as post mitosis state where cells can be in temporary arrest called quiescent, or permanent arrest - senescent
What cells typically remain in g0 for a long time
Neurons, cardiac muscle, rbc
Examples of quiescent cells in g0
Liver cells, lymphocytes, stem cells
FACS
Fluorescence activated cell sorting
Number of chromosomes remains the same in a facs peak one and two
True
Discrete process of cell cycle
Events that only occur at certain points, like replication and mitosis
Continuous processes in cell cycle
Occur through cycle, like nutrient assimilation and cell growth
MPF
Maturation promoting factor
Something In cytoplasm controls entry into mitosis
MPF
Cdk stands for
Cyclin dependent kinase
Active m cdk is also known as
MPF
A kinase is an enzyme that
Phosphorylates target proteins using bound atp
Phosphorylation by kinases results in a
Conformational change that can either activate or inactivate target
Activity of cyclin during cell phase
Accumulates during interphase, reaching a max in mitosis, the rapidly declines at end of mitosis
Proteins that are phosphorylated by m cdks
Histone h1, and condensins
Nuclear lamins
Nucleolin
Srk
Cdc 25
Anaphase promoting complex
Cdk binding to cyclin is ___ but not ____ for enzyme activity
Necessary but not sufficient
CDK turing on via
- Association with cyclin
- Phosphorylation and dephosphorylation of cyclin complex
Once cyclin is bound to cdk phosphates are added and removed based on
Current cellular conditions
Growth inhibitor signal for g2 m checkpoint
Blocking activation of cyclin /cdk
What happens if there is indestructible m cyclin
Cells get stuck in mitosis as degradation can’t happen and MPF stays active, no reset to g1
What helps further packing of interphase chromatin fiber
Condensins
What helps hold sister chromatids together
Cohesins
Structural definition of condensins
Highly processive motors that help to loop dna
What phase do the nucleoli disappear
Prophase
Prometaphase starts
With breakdown of the nuclear envelope so chromosomes can attach to spindle
How do chromosomes attach to spindle
Kinetochores
What triggers phosphorylation of nuclear lamins
Activated m cdk
Three classes of mt making up the mitotic spindle
Astral, kinetochore, interpolar
Interpolar mt function
Stabilize spindle and push poles apart, interact via motor proteins
Astral mt function
Anchors and positions spindle with help of Dynein motors at cortex
Kinetochore attachment is referred to as happening via
Random growth and shrinkage of mt
What makes a kinetochore stable
High tension, attached to sister chromatid from each pole
Mt are shorter and more dynamic in mitotic cells than in interphase cells because
Increased activity of mt depolymerizing proteins to help proper spindle assembly
What is poleward flux
Tubulin is continually added at the plus ends and lost at minus ends so the mt stays the same length as gfp labeled tubulin moves towards pole
Anaphase a
Sister chromatids pulled towards opposite spindle poles and kinetochore mt shortens at plus end. Dynein helps pull chromatids to poles
Anaphase B
Spindle poles themselves move farther apart. Kinesin pushes interpolar mt apart by walking towards plus end
Taxol affects on anaphase a and B
Taxol stabilizes mt. Anaphase a is affected since kinetochore mts cannot depolymerize but in B, interpolar mt can still lengthen
APC inhibition results in
Metaphase arrest
Non degradable m cyclin results in
Anaphase arrest
Telophase is controlled by destruction of
M cyclin
How is m cyclin degraded
Will be tagged with ubiquitin and destined for proteome
How does nuclear envelope reassemble
Lamins become dephosphorylated and and membranes fuse together by nuclear pores associating with one another
What is the difference in cytokinesis in plant cells
Golgi derived vesicles will come together and form a phramogmoplast which develops into a cell plate to form a new cell wall
Cytochlasins effect on mitosis
Bind to plus end of actin filaments and prevent polymerization so cell movement and cytokenisis fail to separate cells
Effect of colchicine on anaphase a and B
A none, as mt is depolymerizing. In B as mt are polymerizing the spindle poles cannot separate as interpolar mt will not form and function correctly
