Sentence:  ... Munoz "et al." first proposed the following <WSD>"scaffold</WSD> filling" problem (on multichromosomal genomes with no gene repetition) as followsnb.... Given a complete (permutation) genome "R" and an incomplete <WSD>scaffold</WSD> "S", fill the missing genes in "R – S" into "S" to have "S′" such that the genomic distance ... between "R" and "S′" is minimized. It was shown that this problem can be solved in polynomial time. 
Meaning of the word marked with <WSD> tags:  A structure that provides support for some other material.