Domain: Natural Science — Cell & Developmental Biology
Target concept: Time-lapse microscopy of animal cells undergoing mitosis and cytokinesis

Video generation prompt: Time-lapse microscopy imaging of individual cultured mammalian cells progressing through mitosis to cytokinesis.

Evaluation guide:
(i) Target concept: Time-lapse visualization of canonical mitotic progression culminating in symmetric cytokinesis in a single mammalian somatic cell.
Minimum mechanism: Chromosome condensation must precede spindle attachment; sister chromatid separation must be coordinated and bipolar; cleavage furrow must initiate only after chromosome segregation and nuclear reformation begin; final abscission must yield two discrete, intact daughter cells.
(ii)Storyline: [Frame 1–2] Interphase cell: flattened, spread morphology, diffuse chromatin. → [Frame 3–4] Prophase onset: cell rounds up, chromatin condenses into discrete rods, nuclear envelope dissolves. → [Frame 5–6] Metaphase: chromosomes align in single plane at cell center. → [Frame 7–8] Anaphase: sister chromatids move synchronously toward opposite poles. → [Frame 9–10] Telophase: chromosomes decondense, nuclear envelopes reform. → [Frame 11–12] Cytokinesis: cleavage furrow forms circumferentially at former metaphase plate and ingresses continuously until two separate daughter cells are resolved. Perspective: fixed top-down view; no rotation, zoom, or tilt; full cell always in frame; background is optically uniform (glass dish + medium).

Manual:
Experimental Procedure
1. Culture fluorescently labeled (e.g., H2B-GFP) mammalian cells (e.g., HeLa or RPE-1) on glass-bottom dish.
2. Mount dish on inverted microscope with environmental chamber (37°C, 5% CO₂).
3. Acquire time-lapse images every 60–90 seconds using phase-contrast or epifluorescence for 10–15 minutes.
Observation of Experimental Phenomena
A single cell rounds up, condenses chromosomes, aligns them at center, separates sister chromatids to opposite poles, reforms nuclei, and forms a cleavage furrow that bisects the cell into two daughters.
Summary of Experimental Principles
Mitosis ensures faithful nuclear division via conserved stages (prophase→metaphase→anaphase→telophase); cytokinesis completes cell division via actin-myosin II contractile ring assembly at the former metaphase plate.

Prompt Grounding rubric:
level_1: No cultured mammalian cell visible; no time-lapse sequence shown; no mitotic stages identifiable; no cytokinesis event present; scene shows unrelated objects (e.g., plant cells, tissue sections, or non-biological material).
level_2: A single mammalian cell is present but static (no progression); at least one mitotic stage label or schematic overlay appears, but no actual morphological change occurs; no temporal progression from prophase to cytokinesis; cell lacks characteristic rounded shape during division.
level_3: A single cultured mammalian cell is visible and undergoes visible morphological changes consistent with mitosis and cytokinesis; all major stages (prophase → metaphase → anaphase → telophase → cytokinesis) appear in correct sequential order; cell remains centered in fixed field of view throughout; no extraneous objects or labels.
level_4: All conditions for score 3 are met, AND the cell exhibits correct spatial features: chromosomes condense visibly during prophase, align at equator in metaphase, separate toward poles in anaphase, decondense in telophase, and cleavage furrow forms symmetrically during cytokinesis; no other cells enter or exit frame; no duplication or fragmentation of the cell body.
level_5: All conditions for score 4 are met, AND the cell maintains consistent size and contrast across all frames; chromosomal mass is fully contained within the cell boundary at all stages; cleavage furrow ingression is continuous and terminates precisely in two distinct daughter cells; no motion blur, flicker, or frame dropout; no background artifacts, dust, or focus shift.

Scientific and Causal Correctness rubric:
level_1: Cell does not resemble a mammalian somatic cell (e.g., shows cell wall, chloroplasts, or irregular multinucleation); no recognizable mitotic events occur; cytokinesis is absent or replaced by fission/scission inconsistent with actin-myosin ring mechanism.
level_2: Cell is mammalian-like but displays scientifically invalid transitions: e.g., chromosomes appear before nuclear envelope breakdown, spindle forms after anaphase, or cleavage furrow forms before telophase completion; daughter cells remain fused or unequal in size without justification.
level_3: All mitotic stages occur in biologically valid order: nuclear envelope breaks down before metaphase alignment; chromosomes segregate synchronously in anaphase; nuclear envelopes reform in telophase; cleavage furrow initiates only after chromosome decondensation begins; two daughter cells form post-cytokinesis.
level_4: All conditions for score 3 are met, AND structural fidelity is maintained: condensed chromosomes appear as discrete rod-shaped bodies (not granular or diffuse); metaphase plate is strictly planar and centered; anaphase separation is bilateral and symmetrical; cleavage furrow is circumferential and constricts radially—not asymmetric or lateral.
level_5: All conditions for score 4 are met, AND causal integrity is perfect: chromosomal condensation precedes spindle attachment; spindle tension correlates with chromosome movement; furrow initiation coincides with central spindle microtubule bundling (visually inferred as midzone density); final abscission yields two intact, non-fragmented, similarly sized daughter cells with intact plasma membranes.

Spatiotemporal Consistency rubric:
level_1: Severe spatiotemporal discontinuity: cell teleports between positions; abrupt scale jumps (>2× apparent size change between consecutive frames); sudden appearance/disappearance of cell or nucleus; lighting shifts polarity (e.g., shadow direction reverses) without cause; frame rate collapse (stutter, freeze, or reverse).
level_2: Moderate discontinuity: cell drifts >⅓ frame width without smooth motion; nucleus relocates independently of cytoplasm; cleavage furrow appears discontinuously (e.g., skips intermediate constriction states); light intensity flickers >3× across sequence; background texture warps or tiles.
level_3: Cell remains within same field of view with continuous, smooth positional transition; nucleus moves cohesively with cytoplasm; cleavage furrow forms via progressive, uninterrupted constriction; lighting and focus remain stable; no object clipping at frame edges; no inter-frame tearing or ghosting.
level_4: All conditions for score 3 are met, AND motion is physically plausible: cell rounding is gradual and isotropic; chromosome movement in anaphase is linear and directional; furrow ingression speed is uniform (no acceleration/deceleration artifacts); no parallax shift between nucleus and cytoplasmic periphery.
level_5: All conditions for score 4 are met, AND zero spatiotemporal deviation: pixel-level continuity in cell contour across all frames; no detectable interpolation artifacts; no edge aliasing or moiré during motion; no temporal aliasing (e.g., stroboscopic freezing of moving chromosomes); no depth distortion (e.g., no unnatural flattening or bulging of 3D cell shape).