Abstract
Despite tremendous advances in long-read sequencing, some structurally complex and repeat-rich genomic regions remain challenging to assemble. Furthermore, we lack tools to assess local assembly quality, making it hard to identify problems and assess progress. Here we develop a new approach "CloseRead" for visualizing local assembly quality and diagnosing errors using multiple metrics. We apply CloseRead to evaluate how well immunoglobulin loci, paradigmatic cases of structurally complex regions, are assembled in 74 state-of-the-art vertebrate genomes. We then show that targeted, local re-assembly can correct the specific errors identified by CloseRead, highlighting the value of an iterative approach to genome assembly.