The Cell Cycle #lec 5 Flashcards
What triggers the destruction of securin during mitosis?
The APC/C triggers the destruction of securin, liberating a protease that cleaves cohesin and initiates separation of the sister chromatids.
What does the APC/C promote the destruction of during late M phase?
The APC/C promotes the destruction of cyclins, leading to Cdk inactivation and dephosphorylation of Cdk targets.
What processes are required for the completion of anaphase?
The completion of anaphase, disassembly of the mitotic spindle, and division of the cell by cytokinesis.
What is the role of M-Cdk in mitosis?
M-Cdk induces the assembly of the mitotic spindle and ensures that each sister chromatid is attached to the opposite pole of the spindle.
What does M-Cdk trigger in terms of chromosome structure?
M-Cdk triggers chromosome condensation, reorganizing sister chromatids into compact, rod-like structures.
What additional processes does M-Cdk promote in animal cells?
M-Cdk promotes the breakdown of the nuclear envelope and rearrangements of the actin cytoskeleton and the Golgi apparatus.
What are the two families of protein kinases that contribute to early mitotic events?
The Polo-like kinases and the Aurora kinases.
What is the function of Polo-like kinase (Plk) in mitosis?
Plk is required for the normal assembly of a bipolar mitotic spindle and phosphorylates proteins involved in spindle pole separation.
What does Aurora-A control during mitosis?
Aurora-A helps control proteins that govern the assembly and stability of the spindle.
What is the role of Aurora-B in mitosis?
Aurora-B controls the attachment of sister chromatids to the spindle.
What is the purpose of condensin during mitosis?
Condensin reorganizes sister chromatids into distinct structures for easier separation during anaphase.
What processes are involved in the chromosomal changes during early mitosis?
Chromosome condensation and sister-chromatid resolution.
What is the structure of the mitotic spindle?
The mitotic spindle is a bipolar array of microtubules that pulls sister chromatids apart in anaphase.
What initiates the assembly of the spindle early in mitosis?
M-Cdk triggers the assembly of the spindle.
What are the two ends of microtubules in the spindle oriented towards?
The minus ends are oriented toward the pole and plus ends are directed outward.
What is the centrosome composed of?
The centrosome consists of pericentriolar material surrounding a pair of centrioles.
What are the three general categories of microtubule-associated proteins?
Nucleating factors, regulatory proteins, and motor proteins.
What is the most important microtubule nucleating factor?
The γ-tubulin ring complex (γ-TuRC).
What happens to γ-TuRCs at the beginning of mitosis?
The number of γ-TuRCs in each centrosome increases greatly in a process called centrosome maturation.
What is the role of augmin in microtubule nucleation?
Augmin anchors active γ-TuRC to the side of a microtubule, resulting in the nucleation of a new microtubule.
How do mitotic chromosomes contribute to spindle formation?
Mitotic chromosomes generate local signals that activate γ-TuRC, promoting microtubule formation.
What is the state of microtubules during mitosis?
Microtubules are in a state of dynamic instability, continually growing or shrinking.
What happens to the average lifetime of microtubules during mitosis?
The average lifetime of microtubules decreases dramatically, particularly for non-kinetochore microtubules.
What regulates microtubule dynamics during mitosis?
Microtubule-associated proteins (MAPs) and depolymerization factors.
