What base is most commonly modified in RNA ?
A second consequence of the presence of the 2' - hydroxyl group is that in conformationally flexible regions of an RNA molecule ( that is , not involved in formation of a double helix ) , it can chemically attack the adjacent phosphodiester bond to cleave the backbone.RNA is transcribed with only four bases ( adenine , cytosine , guanine and uracil ) , but these bases and attached sugars can be modified in numerous ways as the RNAs mature .