Question

Describe the steps of insertion of simple bacterial transposons

Answer 1

The insertion of simple bacterial transposons involves several steps beginning with transposase, which nicks the DNA, excises the transposon, and ligates it to a new DNA site. This is followed by replication to fill in gaps and complete the insertion, resulting in direct repeats of genomic DNA flanking the transposon.

Step-by-step explanation:

The process of transposon insertion in bacteria involves several well-defined steps facilitated by the enzyme transposase. Initially, transposase transcribes the transposon-encoded gene resulting in the formation of the enzyme which is instrumental in initiating the insertion process. The key steps are as follows:

1. Transposase makes a nick at the DNA duplex and trims the 3'OH ends, leading to a staggered cut that excises the transposon.
2. The transposase brings the transposon ends together during this cutting step.
3. The enzyme mediates the insertion of the transposon into a new DNA site by ligating the 3'OH ends of the transposon to the target DNA's 5'OH ends.
4. Replication then fills in the missing bases at the insertion site, producing direct repeats of the host cell's genomic DNA flanking the transposon.
5. Finally, a ligation step completes the transposition by sealing the transposon into the genomic DNA.

This mechanism demonstrates how bacterial transposons can integrate into genomic DNA and potentially alter gene function by interrupting coding sequences or regulatory regions. It is noteworthy that transposons within bacteria are generally silent in nature, likely due to the compact nature of the bacterial genome and its intolerance for the disruptive influence of random insertions.