SSR and Transposition

Question 1

DNA-type elements: Replicative transposition

Answer 1

1. Transposon and target site are nicked on both strand by a transposase enzyme, generating staggered ends.
2. Both DNA molecules form a crossover structures joining ends together
3. The DNA replicated crating a cointegrate -> a single molecule that contains two copies of the transposon
4. Cointegrate is resolved by a resolvase
5. It obtains two individual replicons carrying each one a copy of the transposon

Question 2

DNA-type elements: Non replicative Transposition

Answer 2

1. Transposase is coded by the transposon
2. Two transposases flank the transposon, bind to the inverted terminal repeats and produce a DSB on each side of the transposon. Donor DNA must be repaired
3. Each transposase binds to one end of the transposon and form a loop structure that protects the transposon and moves along the genome
4. Transposases recognize the target site and make two staggered breaks in each side
5. Transposon joins between the single strand ends
6. Gaps are filled and sealed by cell machinery -> geneation of short direct repeats