q-bio.GNApr 30, 2026

CRC-Screen: Certified DNA-Synthesis Hazard Screening Under Taxonomic Shift

Authors: Najmul Hasan

Organizations: University of North Carolina at Pembroke.

Abstract

DNA-synthesis providers screen incoming orders by searching the requested sequence against curated hazard lists. We show that this baseline collapses to a 100% false-flag rate when the hazardous sequence comes from a taxonomic family absent from the reference set: under Conformal Risk Control's certified miss-rate constraint, a low-discrimination signal forces the threshold below the entire test-benign mass. We compose three signals derived from a synthesis order's public annotation: kk-mer Jaccard similarity to known toxins, the trimmed-mean score of a five-LLM judge panel, and cosine similarity to clustered embedding centroids. Fused under a monotone logistic aggregator and calibrated by Conformal Risk Control, the resulting screener certifies E[FNR]α+TV\mathbb{E}[\mathrm{FNR}] \le α+ \mathrm{TV}, where the additive term is the calibration-to-test distribution shift under family holdout (a certified ceiling of 24-49% across folds). Across ten leave-one-taxonomic-family-out folds at α=0.05α=0.05 on UniProt KW-0800 reviewed toxins, the calibrated screener achieves 0% empirical test miss rate on every fold and 0% test false-flag rate on nine of ten folds. The bound's finite-sample slack 1/(ncal+1)1/(n_{\mathrm{cal}}+1) caps the certifiable miss rate at 1.77% on our 200-hazard subsample; reaching procurement-grade α=103α=10^{-3} requires an 18×18\times larger calibration set, which the full reviewed UniProt KW-0800 corpus is large enough to deliver. The binding constraint on certifiable DNA-synthesis screening is calibration data, not algorithms. Code: https://github.com/najmulhasan-code/crc-screen

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