a) Insertion sequence:

• It is a mobile piece of DNA that is capable of inactivating a gene into which it inserts.
• They are believed to be responsible for spontaneous gene mutation in bacteria and bacteriophage.
• When this insertion sequence transposes, this direct repeat remain at the site of insertion in the host chromosome.

b) Transposons:

• It is a DNA Segment capable of changing its location within or between the chromosome.
• They are usually 2000 bp long and carry one or more genes unrelated to their transposability.