design: Frozen fibroblast cell pellets were received from collaborators at the JacksonLaboratory for Genomic Medicine. Ultra High Molecular Weight (UHMW) DNA was extractedfrom approximately 20 million frozen cellsper sample using the NEB HMW DNA Extraction Kitfor Tissues (NEB #T3060), following the ONT recommended gDNA Extraction Protocol(v114_revL_27Nov2022). Library preparation was performed using the ONT Ultra-Long DNASequencing Kit (SQK-ULK114). The libraries were eluted in 810 L EB to accommodate fourlibrary loads across three flow cells per sample, resulting in a total of 12 libraries per sample. Allsamples were run on the PromethION 48 sequencer (PRO-SEQ048) with R10.4.1 Flow Cells(FLO-PRO114M). Flow cells were washed using the ONT wash kit (EXP-WSH004) and reloadedwith fresh libraries every 24 hours, for a total runtime of 96 hours. The experiment wasrepeated a second time with additional flow cells to achieve the target of 30X genomiccoverage with reads greater than 100 kb in length. The data was basecalled with dorado 0.5.3.