Ren et al. (2018). Genomic basis of recombination suppression in the hybrid between Caenorhabditis briggsae and C. nigoni. Nucleic Acid Research.
The cb4 C. briggsae assembly contains 5,997 gaps (represented by ‘Ns’) and 361 contigs not anchored to any chromosome (‘unassigned’). Ren et al. filled 2,304 gaps by replacing ~240 kbs on six chromosomes and partially closed gaps in ‘unassigned contigs’ and extended ~800 kb sequences. This resulted in a total of ~1,040 kb of new sequence data. The authors also anchored 124 of 361 ‘unassigned’ contigs that added ~1.8 Mb back to individual chromosomes.