EX1 Q1 Flashcards
What are the 3 parts of interphase?
G1,S,G2
What happens in G1 phase?
Cell growth
What happens in S phase?
DNA replication
What happens in G2 phase?
the cell grows more, makes proteins and organelles, and begins to reorganize its contents in preparation for mitosis.
What happens in preprophase?
determination of the future plane of division by the prophase band
What happens in prophase?
-Disappearance of the preprophase band
-Spindle fibers appear
-Nuclear membrane disappears
-Chromosomes condense
What happens in metaphase?
-Alignment of chromosomes at the metaphase plate
-Nuclear envelope reabsorbed into a polar ER network
What happens in anaphase?
-Kinetochore spindle microtubules shorten to separate sister chromatids and pull them towards the poles of the cell
What happens in telophase?
-Chromosomes start decondensing
-Nuclear envelope reforms
-Phragmoplast starts to form
What happens in cytokinesis?
-Cell plate formation
-Chromosomes completely decondensed
-Two cells formed
-Sections of the ER cross the cell plate and form the basis of the plasmodesmata
What is MPF (mitosis promoting factor)? Where is it located?
-induces mitosis in eukaryotes
-located in the cytoplasm of M-phase cells
What are the requirements to pass the G1 checkpoint?
-adequate cell size
-sufficient nutrients
-social signals present
-undamaged DNA
What are the requirements to pass the G2 checkpoint?
-successful chromosome replication
-undamaged DNA
-activated MPF is present
What are the requirements to pass the metaphase checkpoint?
-all chromosomes are attached to the spindle apparatus
What is the composition of MPF? What do the two subunits do?
-made of two subunits: a protein kinase and a cyclin
-An enzyme that transfers phosphate groups from ATP to a protein, thus phosphorylating the protein.
-the cyclin acts as a regulatory protein
When is the highest concentration of cyclin recorded?
the start of M phase
What happens when a protein is tagged with Q?
it will be destroyed by a proteasome
Why do the cyclin levels decrease during M phase?
enzymes that were synthesized during anaphase attach Q to the cyclin subunits
What are cyclin-dependent kinases?
-They are enzymes involved in M phase that phosphorylate a wide array of proteins.
-Each phosphorylation event occurs at an appropriate point during the cell cycle, thereby stimulating or inhibiting a particular cellular process involved in cell division.
mitotic cyclins
Activates cdc2 (cyclin), which allows the passage from G2 to mitosis
What are the three steps of S phase?
initiation, elongation, termination
What are cyclins?
Cyclins are cell cycle regulatory proteins that “switches” kinases on and off
What are Cyclin-dependent kinases (Cdk)?
Cyclin-dependent kinases (Cdk) are cell cycle control enzyme kinases that are regulated by cyclins.
Cyclin-dependent kinases (Cdk) regulate the events happening in the cell cycle by ____ and ____ target proteins as a way of activating/deactivating them. However, a Cdk can only be activated if a ____ binds to it.
-phosphorylating
-de-phosphorylating
-cyclin
Drives the G1 - S transition
Cyclin D & Cdk 4,6
Regulation of G1 - S transition
Cyclin E &Cdk 2
Initiation of DNA replication in S phase
Cyclin A & Cdk 2
Transition from G2 to M phase
Cyclin B & Cdk 1
