AP BIOLOGY

Detailed explanation-1: -Explanation: Composite transposons contain one or more protein-coding genes in addition to those required for transposition. Many of the well known composite transposons carry genes for antibiotic resistance. Two of the best known elements are Tn9 (chloramphenicol resistance) and Tn10 (tetracycline resistance).

Detailed explanation-2: -A composite transposon is a mobile genetic element consisting of two insertion sequences (ISs) flanking a segment of cargo DNA often containing antibiotic resistance (AR) genes. Composite transposons can move as a discreet unit.

Detailed explanation-3: -The bacterial transposons belong to the DNA transposons and the Tn family, which are usually the carrier of additional genes for antibiotic resistance.

Detailed explanation-4: -Though transposons provide antibiotic resistance due to the existence of an extra gene on a plasmid, there are chances that transposons can jump from chromosomal DNA to plasmid DNA and vice versa for development of resistance (Wagner, 2006).

Detailed explanation-5: -Transposons may shift from one plasmid to another or from a chromosome to a plasmid and the other way round, causing genes of antibiotic resistance in bacteria to be transmitted. In Gram-negative bacteria, some examples of composite transposons are Tn5, Tn9, Tn10, Tn903, Tn1525, and Tn2350.