TRAP: Tandem Repeat Assembly Program produces improved shotgun assemblies of repetitive sequences

The software commonly used for assembly of shotgun sequence data has several limitations. One such limitation becomes obvious when repetitive sequences are encountered. Shotgun assembly is a difficult task, even for non-repetitive regions, but the use of quality assessments of the data and efficient matching algorithms have made it possible to assemble most sequences efficiently. In the case of highly repetitive sequences, however, these algorithms fail to distinguish between sequencing errors and single base differences in regions containing nearly identical repeats. None of the currently available fragment assembly programs are able to correctly assemble highly similar repetitive data, and we, therefore, present a novel shotgun assembly program, Tandem Repeat Assembly Program (TRAP). The main feature of this program is the ability to separate long repetitive regions from each other by distinguishing single base substitutions as well as insertions/deletions from sequencing errors. This is accomplished by using a novel multiple-alignment based analysis method. Since repeats are a common complication in most sequencing projects, this software should be of use for the whole sequencing community.