FlyBase curator comment: The F{5'} entry in FlyBase is used to denote the partial transposon present in an insertion when it is known that the inserted sequence is a deleted version of the F-element natural transposon (generated during transposition/excision), and where it is known that sequences have been deleted from the 3' end of the F-element. For details of what portion of the original F-element remains for an individual insertion of F{5'}, see the description in the insertion report and/or in any allele reports associated with that insertion.