431 13.2 Transposable elements in prokaryotes Figure 13-9 Structural features of composite and simple transposons. (a) Tn10, an example of a composite transposon. The IS elements are inserted in opposite orientation and form inverted repeats (IRs). (b) Tn3, an example of a simple transposon. Short inverted repeats contain no transposase. Instead, simple transposons encode their own transposase. The repressor is a protein that regulates the transposase gene. found to carry many different kinds of genes in bacteria. What is the mode of action of these plasmids? How do they acquire their new genetic abilities? How do they carry them from cell to cell? It turns out that the drug-resistance genes reside on a mobile genetic element called a transposon (Tn). There are two types of bacter-ial transposons. Composite transposons contain a variety of genes that reside between two nearly identical IS ele-ments that are oriented in opposite direction (Figure 13-9a) and as such, form what is called an inverted repeat (IR) sequence. Transposase encoded by one of the two IS elements is necessary to catalyze the movement
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This note was uploaded on 01/10/2011 for the course BIOL BIOL taught by Professor Johnson during the Spring '08 term at Aberystwyth University.