Optimal conditions for ultra-long sequencing. To achieve optimal ultra-long (UL) sequencing output, the FRA-to-DNA molecule ratio should be 1:1 in a homogeneous solution, verified through accurate cell counting and/or DNA mass measurement. (A) Hypothetical cutting frequency under three conditions of reaction volume and DNA length when the FRA-to-DNA ratio is 1:1. (B) Hypothetical cutting frequency under three conditions of FRA-to-DNA ratio and DNA length when the reaction volume is large. This figure was created with BioRender (https://www.biorender.com).