A segment of DNA which contains the insertion elements at either end but can contain just about anything in the middle (genes, markers, etc.). These types of transposons tend to be very large, and many of them came about when the inner two insertion elements of two smaller transposons stopped working and only the two at the far ends continue to work, so that when the transposon moves, it takes everything in between the two original transposons with it. Some composite transposons are used in genetics experiments; Tn5 and Tn10 are two such composite transposons which have genes that encode resistance to certain antibiotics.