strand 4 Flashcards
What occurs in prophase?
Entry into mitosis (prophase) is driven by M-CDK (cyclin B -CDK1). M-CDK has to be phosphorylated.
Chromosomes condense (this involves the loss of cohesins - which hold sister chromatids together- and the addition of condensins 1 and 2). Cohesins are involved in the interphase structure, and condensins are involved in the mitotic structure.
Kinetochores are made. M-CDK and Aurora B kinase are required to recruit kinetochore proteins.
Spindle starts to form.
Which kinase is involved in removing Cohesins in prophase?
mitotic kinase called Polo.
What occurs in prometaphase?
Microtubule adaptor proteins become active. Ndc80/Nuf2 are MAP which allow microtubules to attach to kinetochores.
Motor proteins (kinesin 5 and dynein) become active.
Nuclear envelope breaks down to allow microtubules to contact chromosomes.
2 examples of kinesin?
Kinesin 5 - forms dimers and crosslinks microtubules- this pushes the microtubules apart.
CENP-E - kinesin which binds to kinetochore and moves kinetochores towards the equators.
what detects bi-orientation of chromosomes?
Aurora B kinase detects bi-orientation by tension. if the microtubules are attached to the wrong kinetochore, Aurora B kinase will phosphorylated Ndc80 and the microtubules will be removed from the kinetochore.
What detects unattached kinetochores?
The spindle checkpoint will detect unattachment. The unattached kinetochores produce The Mitotic Spindle complex (MCC) which inhibits APC/C from degrading M-Cyclin (Cyclin B ) and therefore the cell stays in mitosis.
