Cell cycle (2) Flashcards
what are the 3 major regulatory tansitions that the cell cycle governs ?
- Start/restriction point (in late G1)
- G2/M transition
- Metaphase to Anaphase transition
what happens in in Start/restriction point ?
cell commits cell cycle entry and chromosome duplication
What happens in G2/M transition ?
- early mitotoic events are triggered = chromososme alignment on mitotic spindle in metaphase
what happens in the metaphase-to-anaphase transition ?
- sister chromatid separation stimulated
- completion of mitosis and cytokinesis
What are cyclin-dependent kinases ?
memebers of a protein family of protein kinases which are central componenets of the cell cyle control system
what are Cdk controlled by ?
A complex array of enzymes and other proteins
what is are the most important Cdk ?
cyclins
what are cyclins ?
there is no Cdks if they are not tighlty bound to a cyclin = no protein kinase activity
are Cdk proteins constant ?
they are constant by contrast
are Cdk proteins constant ?
they are constant by contrast
what is the Cdk blocked bt when cyclin hasn’t attached at active site ?
- T-loop
howevwer when cycline binds T-loop moved out the active site and there is partial activation of Cdk2 - helps clyclies to bind more thightly
what are the 4 classes of cyclins that all eukaryotes need ?
- G1
- S
- G2
- M
what do G1/S cyclines do ?
- trigger protectin through Start
- causes to commitment to cell entry
- levels of cyclines fall in S pahse
- they help to govern activities of the G1/S cyclins whic control Start in late G1
what do S-cyclines do ?
- help stimulate chromososme duplication
- remain elevated untill mitosis
- contribute to control of some early mitotic events
what do M-cyclins do in Cdks?
- stimulate entry into mitosis at the G2/M transition
- levels fall mid-mitosis
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