sanger-sim is a free Sanger learning simulator rendering Sanger 1977 ddNTP chain termination + Smith 1986 BigDye 4-color (ABI fluorescence) + capillary electrophoresis (length-based fragment separation) + Gaussian peak chromatogram (σ≈0.4 base width) + Phred Q score (Ewing & Green 1998 Genome Res, Q = −10·log₁₀ Pe, Q20=1% / Q30=0.1% / Q40=0.01%) + heterozygous mixed peak IUPAC ambiguity (R/Y/M, etc.) + poly-A slippage scenario (Gemini advantage #9, polymerase slippage waveform breakdown + Phred red drop) — all in-house SVG, zero npm.

(1) Static undergrad lab manual figures → dynamic chromatogram + Phred Q learning (2) Establish Sanger Phred Q baseline (Q20/Q30/Q40 meanings) before NGS (3) Heterozygous IUPAC ambiguity (R/Y/M) variant analysis baseline (4) Intuit poly-A repeat sequencing limits (polymerase slippage) — caution for clinical variants (5) Trim recommendation past 700 nt where Q20 fails (Claude advantage #6) (6) Zero external libs

① Enter template DNA (50-1000 nt) + noise slider (0-50%) ② ddNTP termination simulation → fragments separated by length ③ Capillary electrophoresis SVG → 4-color fluorescent chromatogram auto-renders ④ Gaussian peak σ≈0.4 base width per position → base call (max of 4 colors) ⑤ Phred Q auto-calculated — Q40 (1/10000 error) vs Q20 (1/100) ⑥ Heterozygous toggle → position 30 mixed peak (50:50 A+G → IUPAC R) ⑦ Poly-A slippage toggle → AAAAAAAAAA causes waveform breakdown + Phred red drop ⑧ Auto trim box past 700 nt (Q20 fail) ⑨ Hover 16 academic terms (ddNTP / chain termination / capillary electrophoresis / Phred / base call / heterozygous / BigDye / IUPAC ambiguity / slippage, etc.)

Example 1) Clean single peak (0% noise) → 100% base call + Q40 Example 2) Heterozygous 50:50 at position 30 → IUPAC R (A+G) + Q20-30 Example 3) 30% noise chromatogram → Phred Q15-20 (qualitative match, Ewing 1998) Example 4) Past 700 nt with Q20 fail → trim recommendation box Example 5) Poly-A AAAAAAAAAA → polymerase slippage waveform breakdown + Phred red drop (5th learning scenario)