Domain: Natural Science — Biochemistry & Molecular Biology
Target concept: Ethanol precipitation of genomic DNA, resulting in the formation of visible white filamentous material

Video generation prompt: In the laboratory, cold ethanol was carefully layered over the clarified microbial lysate in a transparent test tube, and a glass rod was slowly rotated at the interface between the two phases.

Evaluation guide:
(i) Target concept: Interfacial nucleation of DNA precipitate induced by mechanical agitation during ethanol precipitation.
Minimum mechanism: Ethanol is fully miscible with the aqueous lysate, but careful slow layering exploits the density difference between the two liquids so a transient two-layer interface persists long enough to be used; DNA is soluble in the aqueous lysate but comes out of solution once the local ethanol concentration near the interface rises past a threshold, so it precipitates preferentially at/near that interface; rotating a glass rod at the interface locally concentrates and draws the precipitating DNA together into visible filaments before the layers fully mix.
(ii)Storyline: Frame 1–2: Static view of two-layer system (amber lysate below, colorless ethanol above) in transparent tube, glass rod poised above interface. Frame 3–4: Glass rod descends and contacts interface. Frame 5–8: Continuous unidirectional rotation at interface; white filaments emerge *only* at contact zone and wrap around rod. Frame 9–10: Rotation stops; filaments remain coiled and intact on rod, no dispersion. Viewpoint is fixed frontal, centered, with full tube height and interface fully in frame throughout; no occlusion, no hand entry, no secondary actions.

Manual:
Experimental Procedure
1. Place a transparent test tube containing clarified pale yellow-to-amber microbial lysate on bench.
2. Carefully layer ice-cold ethanol over lysate to form a distinct upper colorless layer.
3. Insert a clean glass rod vertically so its tip rests precisely at the interface.
4. Slowly rotate the glass rod at the interface for ~5 seconds.
Observation of Experimental Phenomena
White filamentous DNA precipitate forms exclusively at the interface and adheres to the rotating glass rod as bright white, opaque, thread-like strands.
Summary of Experimental Principles
Cold ethanol reduces DNA solubility and dehydrates nucleic acid molecules, causing them to aggregate and precipitate as visible white filaments—especially when nucleation is promoted at the liquid–liquid interface via mechanical agitation.

Prompt Grounding rubric:
level_1: No transparent test tube visible; no microbial lysate layer present; no ethanol layer present; no glass rod present; no interface between two liquids visible; no rotation action happening.
level_2: A test tube with at least one liquid is present, but there's no clear two-layer system of lysate and ethanol, or a glass rod is present but never reaches any interface, or no rotation is shown at all.
level_3: The test tube shows two stacked layers (a lower amber lysate layer and an upper colorless ethanol layer) with a visible boundary between them; a glass rod touches that boundary; rotation of the rod is visible but only partial or intermittent, or not clearly centered on the boundary.
level_4: The tube holds two distinct, horizontally stacked layers (amber lysate below, colorless ethanol above, fully covering the lysate); a glass rod is inserted vertically with its tip continuously touching the boundary between the layers; the rod turns smoothly and continuously right at that boundary without dipping up into the ethanol or down into the lysate.
level_5: All 4-point conditions are met, and additionally the boundary between the two layers stays sharply defined with no cloudiness or mixing, the rod is thin and clear with no visible distortion, rotation proceeds at a steady, unhurried pace around a fixed vertical axis, no hands or extra objects ever enter the frame, and the camera stays fixed and centered on the tube so the full height of both layers and the full rod are visible throughout.

Scientific and Causal Correctness rubric:
level_1: No white filamentous material ever appears; nothing in the video visually represents DNA precipitating; the two layers either merge instantly or sit inert with no visible response to the rod's rotation.
level_2: White filaments appear, but not where the rod meets the boundary (e.g., they show up floating loose within the amber layer, or stuck to the tube wall away from the rod), or the material looks gray or translucent rather than bright, opaque white.
level_3: Bright white, opaque, thread-like filaments appear at the boundary only during or after rotation and cling to the glass rod; nothing forms before the rod starts turning.
level_4: All 3-point conditions are met, and additionally the filaments form only right at the boundary band itself (not spreading up into the ethanol or down into the lysate), and they stay wound on the rod without falling off, dissolving, or clouding the surrounding liquid for the rest of the clip.
level_5: All 4-point conditions are met, and additionally the filaments are evenly thick and uniformly opaque white with no thin or translucent patches, they wind smoothly around the rod without kinking or breaking, no stray particles or bubbles appear anywhere else in either layer, and the wound mass of filament stays clearly visible even after the rod stops turning.

Spatiotemporal Consistency rubric:
level_1: Severe violation: the tube vanishes or jumps to a new location, the two layers disappear and reappear with no pouring shown, the glass rod jumps position with no travel path shown, rotation snaps on or off with no visible turning motion, or the room lighting suddenly changes.
level_2: Moderate violation: the tube shifts sideways by more than its own width between shots, the boundary line disappears for a stretch and then reappears, the rod flickers in and out of view, or the rotation reverses direction or stops-and-restarts repeatedly.
level_3: One minor flaw only: e.g., the tube drifts a little (less than about half the tube's width) but stays upright and centered, the boundary ripples briefly but resettles flat, the rod stays visible the whole time, or the rotation continues in one direction but its speed varies slightly.
level_4: The tube stays fixed in place and orientation; the boundary stays flat and level except right where the rod stirs it; the rod only spins about its own vertical axis with no sideways drift or tilt; nothing freezes, tears, or ghosts on screen.
level_5: All 4-point conditions are met, and additionally the tube's glass reflections and the amber/colorless liquid colors stay consistent with one fixed camera angle and steady lighting throughout, the curved liquid surface at each layer looks physically normal and doesn't change shape unexpectedly, and the background stays in place and evenly lit for the whole clip.