Card Set Information
G0 phase can be an alternative to
Self-destruction by apoptosis
Anchorage-dependent cells are those
That will grow and proliferate normally as long as they are properly attached to the extracellular matrix.
Contact inhibition is when
Cells will stop growing and proliferating when they come in contact with each other, signaling that the space if filled.
Cancer cells differ in regulation of their growth in that
They can proliferate in a mitogen, anchorage, and contact inhibition-independent manner and are referred to as being immortal.
A mitogen is a
chemical substance that encourages a cell to commence cell division, triggering mitosis
Cells in the G0 stage are activated by growth factors that
turn on cyclin D which binds to cyclin dependent kinases (Cdks) to activate them.
Two key classes of regulatory molecules determine a cell’s progress through the cell cycle.
What is the difference between cyclins and cyclin-dependent kinases
– synthesized at specific stages of the cell cycle
– regulatory subunits
– no catalytic activity
Cyclin-dependent kinases (CDKs)
– are constantly expressed
– catalytic subunits
– inactive in the absence of a partner cyclin
– phosphorylates proteins to activate or inactivate them
What determines the downstream proteins targeted in the cell cycle
Different cyclin-CDK combinations
The cyclin that binds to Cdk2 and is the primary molecule responsible for the progression of S phase is
G1 phase occurs
From the end of the previous M phase until the beginning of DNA synthesis
DNA is 2n - two sets of chromosomes present
What happens in the G1 phase
Great amount of protein synthesis
–Enzymes required in S phase
Mainly those needed for DNA replication
New organelles are being synthesized
During the G1 phase, safeguards exist as proteins known as
Cyclin-dependent kinases (CDKs)
The G1 CDK proteins activate
transcription factors for a variety of genes
Phosphorylation of what by a cyclin/Cdk is essential to get beyond the G1 restriction point
Rb and Rb-p represent the unphosphorylated and the phosphorylated forms of the
In G0 and early G1, Rb physically associates with what and blocks their transactivation domain.
In late G1, Rb-p releases E2F, allowing
the expression of genes that encode products necessary for S-phase progression.
What is true about the relationship between Rb and E2F?
Phosphorylated Rb cannot bind to E2F
What phase in mitosis has a check point
Cyclin-CDK complexes are
heterodimeric protein complexes that regulate cell cycle progression
The activity of the cyclin-CDK complexes is tightly regulated because
They are responsible for cell cycle progression and inducing cellular growth and proliferation
The cyclins are targeted for degradation by
The ubiquitin-proteasome system
G2 phase is from
End of S phase until the cell enters mitosis
Entry into mitosis
Significant biosynthesis occurs during this phase mainly
Production of microtubules
Inhibition of protein synthesis during G2 phase
prevents the cell from undergoing mitosis.
MPF promotes the entrance into mitosis from the G2 phase by
phosphorylating multiple proteins needed during mitosis.
Mitosis promoting factor (MPF)
Stimulates the mitotic and meiotic cell cycles.
Mitosis promoting factor (MPF) is activated by
If DNA is damaged, the cell cycle is arrested via inactivation of
What is the function of Cdc25
It is a phosphatase that activates MPF and CDK
MPF activity is related to the concentration of
cyclins (esp. cyclin A and B)
What is the function of Wee1
It phosphorylates cyclin B/Cdk1 to keep it inactive. And inhibits CDK
Strictly speaking, cytokinesis is not part of
Mitosis but is an event that directly follows mitosis in which cytoplasm is divided into two daughter cells.
Cytokinesis is process that
Divides the nuclei, cytoplasm, organelles and cell membrane into two cells
Kinetochores are attached
to spindle fibers which are attached to centrosomes
Securin is a protein involved in
control of the metaphase-anaphase transition and anaphase onset (Securin inhibits separase)
Separase is a cysteine protease responsible for
triggering anaphase from metaphase
Cohesin is the protein complex responsible for
binding the sister chromatids during S phase, through G2 phase, and into M phase.
The lack of cyclin B allows
The anaphase promoting complex (APC) to form, which breakdowns securin
The cell cycle can be divided into 2 phases
an I (interphase) and a M (mitotic) phase.
During interphase the cell
grows, replicates its DNA and prepares for cell division
Interphase can be divided into what three phases
G0 (a resting phase), G1 (a cell growth phase, S (a DNA synthesis phase) and G2 (prep for mitosis)
The CDKs are inactive unless
bound to a cyclin
When they are bound to a cyclin, the CDKs
phosphorylate other proteins to drive the cell forward through the cell cycle.
What three stages have a check point
G1 G0 M