The Cell Division Cycle

These flashcards cover key concepts from Chapter 18 of the lecture notes on the cell division cycle, focusing on cell cycle control, stages, and apoptosis mechanisms.

What are the major stages of the eukaryotic cell cycle?

The eukaryotic cell cycle contains four phases: M phase (mitosis and cytokinesis) and interphase (including G1, S, and G2).

What does the G1/S transition in the cell cycle entail?

Mitogens stimulate cell division by promoting the synthesis of G1 and G1/S cyclins, leading to DNA synthesis and chromosome duplication.

What is the role of cyclin-dependent kinases (Cdks) in the cell cycle?

Cdks are enzymes that must be bound to cyclins to be active; they phosphorylate target proteins to promote progression through the cell cycle.

How do cyclin levels regulate the cell cycle?

Cyclin levels fluctuate throughout the cell cycle, and their concentrations are regulated by transcription and proteolysis.

What is the function of the anaphase-promoting complex (APC)?

APC triggers the degradation of cyclins, thereby regulating the transition from metaphase to anaphase during mitosis.

What is apoptosis and when does it occur?

Apoptosis is programmed cell death that eliminates unwanted cells and occurs frequently during development and maintenance of tissue homeostasis.

What are some features of apoptosis?

Features of apoptosis include cell shrinkage, nuclear envelope disassembly, DNA fragmentation, and recruitment of phagocytic cells.

What triggers the intrinsic apoptotic pathway?

The intrinsic pathway is triggered by factors like DNA damage or stress, leading to the release of cytochrome C from mitochondria.

What is the role of retinoblastoma (Rb) protein during the cell cycle?

Rb inhibits S-phase entry by preventing the expression of proliferation-related genes and is inactivated by Cdks via phosphorylation.

How can DNA damage affect the cell cycle?

DNA damage can arrest the cell cycle in G1, allowing time for repair, and activate p53, which can induce apoptosis if damage is extensive.