TALEN Gene Editing: RVD Code & FokI Dimerization

TALENs (Transcription Activator-Like Effector Nucleases) are a gene-editing platform built before CRISPR became dominant, and they read DNA differently: each protein repeat in a TALE array recognizes exactly one base pair via its repeat-variable diresidue, giving a simple one-repeat-to-one-nucleotide code instead of CRISPR's guide-RNA base pairing. This simulator renders a 3D DNA double helix and lets you design a matched left/right TALE array around a randomized target sequence, dial in the spacer length between the two half-sites and the number of RVD mismatches, then attempt cleavage. Because FokI only cuts as a dimer, the two nuclease domains must land within a real dimerization window — the simulation checks that window and the RVD match quality live, reports an estimated genome-wide off-target count from the matched-repeat count, and visibly splits the helix only when both conditions are actually satisfied.