Overview of the Eukaryotic Cell Cycle and Regulation

Primary function of the cell cycle

The cell cycle ensures accurate duplication and distribution of a cell's genome.

Major phases of the eukaryotic cell cycle

G1, S, G2, and M (mitosis).

Cyclin-dependent kinases (Cdks)

Protein kinases that regulate the cell cycle when bound to cyclins.

Gene product responsible for the G2 to M transition

cdc2 gene product, which is a protein kinase.

Regulators of Cdk-cyclin complexes

Phosphorylation and dephosphorylation at specific sites.

Targets of mitotic Cdk-cyclin phosphorylation

Nuclear lamins (nuclear envelope breakdown), Condensin (chromosome condensation), and MAPs (mitotic spindle assembly).

Role of the Anaphase Promoting Complex (APC)

Triggers anaphase by degrading mitotic cyclin and securing proteins.

Mad and Bub proteins regulation of the metaphase checkpoint

They inhibit Cdc20, preventing APC activation until all chromosomes are attached.

Role of p53 in the cell cycle

Acts as the "Guardian of the Genome"; triggers cell cycle arrest or apoptosis upon DNA damage.

Effect of p53 phosphorylation

It dissociates from Mdm2, becomes stabilized, and acts as a transcription factor.

Protein often defective in over 50% of human cancers

p53.

Proteins that mediate apoptosis

Caspases - exist as inactive procaspases and become activated to execute cell death.

Distinction between apoptosis and necrosis

Apoptosis is controlled, involves blebbing and cell fragmentation, and does not harm neighboring cells.

Use of temperature-sensitive yeast mutants

Studying the cell cycle—show normal growth at permissive temperatures and arrest at higher temperatures.

Function of the Ras pathway in cell signaling

Activates a phosphorylation cascade (Raf → MEK → MAPK) that promotes cell division.