The insertion of twenty nucleotides immediately after the stop codon would likely disrupt the formation of the attenuator stem-loop structure.

Interfere with the ability of the RNA polymerase to read the trpL region and form the appropriate secondary structures necessary for attenuation.

Insertion of twenty nucleotides could potentially alter the reading frame of the trpL region, resulting in a different amino acid sequence being translated.

Formation of functionally normal protein/polypeptide with no change in the gene expression as the nucleotides are added after the stop codon.