Correct option is B
Explanation-
Statement A: "Transposons have inverted terminal repeats and their integration generates inverted repeats at the flanks of the target site in the host genome." - Partially incorrect
Transposons do have inverted terminal repeats (ITRs). However, integration creates direct repeats (not inverted) of the target site, known as target site duplications (TSDs). So this statement is incorrect due to the error about the nature of repeats at the target site.
Statement B: "A composite transposon can transpose as a unit." - Correct
Composite transposons consist of two insertion sequences flanking other genes (like antibiotic resistance). These elements can move as a unit. So this is correct.
Statement C: "The transposition event may cause deletions or inversions or move a host sequence to a new location." - Correct
Transposition can lead to genomic rearrangements, including deletions, inversions, and even movement of adjacent host sequences, especially in replicative transposition. This is correct.
Statement D: "The transposition event may cause deletions or inversions but cannot move a host sequence to a new location." - Incorrect
This contradicts statement C. Some transposons, like composite ones, can mobilize adjacent host DNA during aberrant events. So D is false.
Statement E: "Replicative transposition proceeds through cointegration." - Correct
In replicative transposition, the transposon is copied, and a cointegrate is formed temporarily, which is later resolved. So E is correct.
Correct statements: B, C, and E
Thus, the correct option is: Option b: B, C, E
