Cell Cycle Part 3

Interphase

The phase of the cell cycle where the cell grows, performs its normal functions, and prepares for cell division. It consists of G1, S, and G2 phases.

G1 phase

The first phase of interphase, where the cell grows in size, synthesizes proteins, and prepares for DNA replication. organelles are duplicated

S phase

The phase of interphase where DNA replication occurs, leading to the synthesis of an identical copy of the genome.

G2 phase

The final phase of interphase, during which the cell continues to grow and prepares for mitosis.

Start/restriction point

A checkpoint in the G1 phase of the cell cycle where the cell commits to entering the cell division cycle and proceeding into S phase.

G1 cyclin/CDK

A complex of G1 cyclin and cyclin-dependent kinase (CDK) that promotes progression through the G1 phase of the cell cycle and prepares for DNA replication.

G1/S cyclin/CDK

A complex of G1/S cyclin and CDK that functions to push the cell from G1 into the S phase, initiating DNA replication.

S cyclin/CDK

A complex of S cyclin and CDK that regulates the S phase of the cell cycle, ensuring proper DNA replication.

M cyclin/CDK

A complex of M cyclin and CDK that regulates the progression of the cell into and through mitosis, ensuring proper cell division.

Mitogen

A signaling molecule that stimulates a cell to undergo cell division by promoting the G1/S transition in the cell cycle. It activates G1-CDK

Phosphorylates

After mitogen binds to the receptor, activated G1-Cdk __________ Rb, which inactivates it

Retinoblastoma/Rb

A tumor suppressor protein that regulates the cell cycle by binding and inhibiting E2F transcription factors, controlling the G1/S transition.

p27

A CDK inhibitor that regulates cell cycle progression by inhibiting the activity of cyclin/CDK complexes, particularly during the G1 phase.

SCF

A ubiquitin ligase complex that targets p27 for degradation via the ubiquitin-proteasome pathway

Pre-replicative complex

A protein complex that forms at the origin of replication during the G1 phase to initiate DNA replication in the S phase, consists of ORC and licensing factor

Cdc6

Licensing factor involved in the initiation of DNA replication by forming part of the pre-replicative complex and also controlling when/where replication origin begins

Origin recognition complex/ORC

A protein complex that binds to the origin of replication during the G1 phase to initiate DNA replication, activated by being phosphorylated by S-Cdk

Checkpoint

A control mechanism in the cell cycle that ensures that each phase is completed accurately before the next phase begins.

Mad2

Protein that gets phosphorylated if there’s a lack of tension at any kinetochore which activates a pathway that keeps Cdc20-APC inactive

p53

A tumor suppressor protein that regulates the cell cycle and promotes apoptosis in response to DNA damage, activated once phosphorylated and promotes p21 production

p21

A CDK inhibitor that is activated by p53 and inhibits the activity of G1/S and S cyclin/CDK complexes to halt the cell cycle, particularly during DNA damage response.

Necrosis

A form of cell death that occurs due to external damage, very messy cell death

Apoptosis

Programmed cell death that occurs in a controlled manner, playing a key role in tissue homeostasis and development.

Caspase

A family of proteases that play essential roles in apoptosis by cleaving specific proteins that lead to cellular breakdown.

Procaspase

An inactive precursor form of caspases that is activated during the process of apoptosis.

Caspase cascade

A series of activated caspases that amplify the apoptotic signal, leading to systematic dismantling of the cell.

Extrinsic pathway

pathway for inducing apoptosis triggered by external signals like death ligands binding to cell surface receptors

Intrinsic pathway

main pathway for inducing apoptosis triggered by internal signals, often in response to cellular stress or damage, such as DNA damage.

necessary

Phosphorylation of Rb ______ to pass the restriction point

G1/S, S phase cyclins and CDKs

Phosphorylation of Rb allows expression of proteins required for DNA replication including _______ and ________