Question

Cutting at the LTR repeats of provirus DNA by integrase results in ___' recessed ends?

1) 3'
2) 5'
3) 3' and 5'
4) cannot be determined

Answer 1

Cutting at the LTR repeats of provirus DNA by integrase results in 3' recessed ends. This enzymatic activity by integrase exposes the 3' hydroxyl group, which is essential for the integration of retrotransposons.

Step-by-step explanation:

The question pertains to the cutting at the LTR (Long Terminal Repeats) of proviral DNA by the enzyme integrase and the nature of the recessed ends that result from this enzymatic activity.

When integrase cleaves the LTR regions during the process of retrotransposon integration, it creates 3' recessed ends. This is because integrase catalyzes the hydrolysis of DNA, cutting off the phosphate backbone near the 5' end of the DNA, leaving the 3' hydroxyl group exposed. These free 3' hydroxyl ends then prime replication for the integration of retrotransposons such as LINEs (Long Interspersed Nuclear Elements) into the genomic DNA.