Ninja Nerd :Cell Cycle, Interphase & mitosis

Cell Cycle

Ordered series of events leading to cell division, consisting of interphase (G1, S, G2) and M phase (mitosis + cytokinesis).

Interphase

The preparatory phase of the cell cycle; includes G1 (growth), S (DNA synthesis), and G2 (prep for mitosis).

S Phase

Synthesis phase where DNA is replicated, producing two identical sister chromatids per chromosome.

Cohesin

Protein complex that holds sister chromatids together at the centromere until anaphase.

Centrosome

Microtubule-organizing center that duplicates during interphase and forms the two poles of the mitotic spindle.

Mitosis

Division of the nucleus; divided into prophase, prometaphase, metaphase, anaphase, and telophase.

Kinetochore

Protein structure assembled on the centromere; attachment site for spindle microtubules.

Metaphase Plate

The equatorial plane where chromosomes align during metaphase.

Separase

Protease that cleaves cohesin, triggering sister chromatid separation in anaphase.

Cleavage Furrow

Actin-myosin ring constriction in animal cells that pinches the cell into two during cytokinesis.

Cell Plate

Structure formed from Golgi-derived vesicles that fuses at the equator of plant cells, eventually becoming the new cell wall.

Cyclin-Dependent Kinase (CDK)

Enzyme that, when bound to a cyclin, phosphorylates target proteins to drive cell cycle progression.

MPF (Maturation Promoting Factor)

Cyclin B/CDK1 complex that triggers entry into mitosis; activated by Cdc25 dephosphorylation.

Wee1 Kinase

Enzyme that adds inhibitory phosphates to CDK1, keeping MPF inactive until the G2/M checkpoint is passed

p53

Tumor suppressor protein that halts the cell cycle in response to DNA damage and can initiate apoptosis.

Retinoblastoma Protein (Rb)

Tumor suppressor that inhibits E2F; when phosphorylated, releases E2F to promote S-phase entry.

APC/C (Anaphase Promoting Complex/Cyclosome)

E3 ubiquitin ligase that targets securin for degradation, leading to separase activation and anaphase onset.

Spindle Assembly Checkpoint

Surveillance mechanism that prevents anaphase until all chromosomes are properly attached to the spindle.