Transposons as Vectors, Activator Dissociation System, Transposase Enzyme, Drosophila

	Transposons as Vectors Transposons of higher plants (Ds, Ac or Mu 1 of maize). Ac and Ds are popular transposons in corn, and were earlier known to represent activator dissociation (Ac-Ds) system. Each represents a transposon with short terminal repeats enclosing a long DNA segment, which measures more than 4500 bp in Ac and about 400 bp in Ds.
Each possesses genes including the gene for transposase enzyme responsible for transposition. Part of this region can be deleted and the transposon can be used for cloning of foreign DNA segment in much the same way as in other cases.Transposons of Drosophila (P elements) P element of Drosophila consists mainly of 31 bp (base pairs) terminal inverted repeats enclosing a 3 kilobase protein coding region, coding for transposase and a repressor of transposition. Many internally deleted P elements are also found, where the transposase derived from other complete P elements help their mobilization. In these deleted. P elements, gene for transfer can be inserted to yield recombinant P element, which can be microinjected into the fertilized egg, along with normal P element (helper P to supply transposase).The inserted gene is transposed onto an embryonic chromosome.