Final answer:
A transposon is the structural element that only needs to carry enzymes needed for transposition. Transposons are genetic elements that can independently move within a DNA molecule or between different DNA molecules, introducing genetic diversity.
Step-by-step explanation:
The structural element that only needs to carry enzymes needed for transposition is a transposon. Transposons are genetic elements that can independently move within a DNA molecule or between different DNA molecules, introducing genetic diversity. They contain special inverted repeat sequences at their ends and a gene encoding the enzyme transposase, which is required for transposition. One example of a transposon is the Ac element, which has the gene for transposase and can undergo independent transposition.