PROKARYOTIC TRANSPOSONS

Define Prokaryotic transposons with diagram.

Although the presence of transposons was predicted in Eukaryotes but first observation at molecular level was done in bacteria. Which is a Prokaryote. Bacterial transposable elements are of following types:

A) Insertion sequence or Is elements:

They are the transposable sequence which can insert at different sites in the bacterial chromosomes.  Is elements contains ITRs (inverted terminal repeats) these were first observed in E.coli. The term ITRs implies that the sequence at 5' end of one strand is identical to the sequence at 5' end of the other strand but they run in opposite direction.

B) Prokaryotic transposon element:

These are also called composite transposons and are shown by symbol "Tn".  These are large transposons which are formed by capturing of an immobile DNA sequence within two insertion sequences thus enabling it to more.

Eg:  Tn1, Tn5, Tn9, Tn10, etc..




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