Cell Cycle

Ordered sequence of events duplicating and partitioning the cell: G1 → S (DNA replication) → G2 → M (mitosis + cytokinesis). Checkpoints…

Regulatory subunit whose cyclic synthesis + degradation paces the cell cycle. Cyclin D (G1), E (G1/S), A (S/G2), B (M). Bind and activate…

Ser/Thr kinase active only when bound to cognate cyclin + T-loop phosphorylated + CKI-unbound. CDK1 (MPF, mitosis), CDK2 (S-phase), CDK4/6…

Chromosome partitioning via microtubule-based spindle: prophase → prometaphase → metaphase (bi-orientation) → anaphase (sister-chromatid…

Specialised division producing 4 haploid gametes from one diploid cell via two successive divisions. MI: homologous pairing + crossing over…

Surveillance mechanism delaying anaphase until every kinetochore is bi-oriented. Unattached kinetochores produce MCC (Mad2, BubR1, Bub3)…

'Guardian of the genome': transcription factor activated by DNA damage, hypoxia, oncogene stress. Induces cell-cycle arrest (p21),…

CycD-CDK4/6 phosphorylates Rb, releases E2F, drives S-phase genes. Restriction point: commit to division. Rb loss (retinoblastoma) bypasses…

DSBs activate ATM → Chk2 → p53; stalled forks activate ATR → Chk1. Halt cycle, recruit repair, or apoptose. Tumor-suppressor network.

E3 ubiquitin ligase that polyubiquitinates securin and cyclin B, triggering sister-chromatid separation and mitotic exit. Cdc20 + Cdh1…