AP Biology Unit 4: Cell Communication and Cell Cycle — Tips & Strategies

The cell cycle has three major checkpoints: G1 (growth check), G2 (DNA replication check), and M (spindle assembly check). Mutations in checkpoint genes can lead to cancer.

Mitosis produces 2 identical diploid cells (growth/repair). Meiosis produces 4 genetically unique haploid cells (gametes). Know the purpose, chromosome number, and genetic variation for each.

All signal transduction follows: Reception (ligand binds receptor) -> Transduction (relay molecules amplify signal) -> Response (cellular change). Use this framework for every signaling FRQ.

Negative feedback reduces a stimulus (maintains homeostasis). Positive feedback amplifies a stimulus (drives processes to completion). Most biological systems use negative feedback.

Apoptosis is a controlled, orderly process that eliminates damaged or unneeded cells. It is essential for development, immune function, and preventing cancer. Don't confuse it with necrosis.