Question

Which of the following is a key difference between replicative and non-replicative transposition?

A. In non-replicative transposition, the gene is deleted from the genome, and in replicative transposition the original copy of the gene is inverted.

B. In non-replicative transposition, the transposition event occurs during mRNA processing, and in replicative transposition the transposition event is stimulated by RNA polymerase.

C. In non-replicative transposition, the gene is deleted from its original location, and in replicative transposition one copy of the gene always remains at the original site.

D. In non-replicative transposition, multiple copies of the gene are found, and in replicative transposition only one copy of the gene remains.

Answer 1

Ans) The correct answer is "C" i.e in non-replicative transposition,the gene is deleted from its original location,and in replicative transposition one copy of the gene always remains at the original site.

Non.replicative transposition is also known as Cut and paste mechanism.In this type,the transposon creates a double stranded break at the donor site (or original location) of the DNA and moves to the recipient (new site) DNA.The double stranded break in the original site is later repaired by using DNA repair enzymes like DNA glycosylases via Base excision repair mechanism etc.It requires only transposase enzyme.Examples are Tn 5 and Tn10 transposons.

Replicative transposition is also known as Copy and paste mechanism because the Transposon present in the original site gets replicated and inserted in the new site (recipient) of DNA.It requires both transposase enzyme and recombinase enzyme.In this type of transposition,no double stranded break in the original site will occur i.e the transposon present in the original site will not get removed or deleted unlike Non-replicative transposition.Example of Replicative transposition is Tn3 transposon.

IS 1 and IS 903 can use both replicative and non-replicative pathways.

By this information,you can eliminate option "A"and "D"

The option "B" is incorrect. (Transposition will not always occur.It is a rare event.If it will always occur like during RNA processing,due to transposition it can create mutations and may have high impact on the size of many genomes).