GelJockey reads a gel photo and estimates how much DNA is in each sample lane, as a rough ng/µL range. It exists to flag samples that may be too concentrated or too dilute for a sequencing provider — it is not a certified concentration.

Step by step

1. Open your gel. Drag an image onto the box, or click “Open image”. JPEG and PNG always work; a 16-bit TIFF gives the best quality (needs internet the first time, to load the TIFF decoder). RAW/DNG isn’t supported in the browser — export a TIFF or JPEG first.
2. Check the crop. GelJockey auto-finds the gel. If the boxes look wrong, drag a rectangle on the image to crop tightly around just the sample lanes and the ladder, and it re-detects inside that region.
3. Verify the boxes before trusting any number: green = sample bands, orange = the ladder, red = the one reference band used as the standard. Confirm every sample has a single box sitting on its band, and that the red box is on your bright reference band.
4. Fix anything wrong (optional). Click “✎ Edit boxes”, then: drag empty space to add a box, drag a box to move it, drag a corner to resize, select a box and press Delete to remove it, or use “Make ladder / Make sample” to relabel one. Your edits are protected — nothing re-runs auto-detection without asking first.
5. Set your numbers in Settings: the reference band mass (the ng in your bright ladder band — default 160), the sample load in µL, and the range factor.
6. Read the result. Each sample shows a central estimate and a range. Trust the range, not the central number.
7. Export. “Download CSV” for the raw values, or “Print / Save report (PDF)” for a one-page sheet to send to your provider.

What the controls do

Signal channel — which color carries the DNA glow (green for a blue-light transilluminator, red for UV/EtBr). Reference band mass — the known ng in the single bright ladder band used as the standard. Sample load — µL loaded per lane, used to turn ng into ng/µL. Range factor — how wide the ± estimate is (2 means half to double). Ladder = lane with ≥ N bands — how many bands a lane needs before it’s treated as the ladder rather than a sample. Lane spacing — leave at 0 (auto); only nudge it if lanes are being missed.

If detection looks wrong

Missing or merged sample lanes: crop tighter around the band row, or nudge the Lane spacing slider toward your lane-to-lane pitch. Ladder not found: turn on Edit boxes, select the reference band’s box, and press “Make ladder”. “Reference band saturated”: the brightest band is blown out and its true value is lost — retake the photo with less exposure. No numbers at all: there’s no ladder box yet — label one.