Frameshift mutations: AUG and CGG. Hence the correct option is a and d.
A frameshift mutation occurs when the genetic sequence's reading frame undergoes changes due to the insertion or deletion of nucleotides. In the given options, it's essential to note that AUG serves as the start codon, typically initiating protein synthesis rather than causing a frameshift mutation. Conversely, CGG, representing a specific nucleotide sequence, could induce a frameshift mutation if nearby nucleotides are inserted or deleted.
For instance, the insertion of an extra nucleotide after the CGG sequence or the deletion of a nucleotide from the sequence can disrupt the reading frame. This disruption may lead to an entirely different downstream sequence, influencing the encoded amino acids and potentially resulting in a nonfunctional or modified protein. Frameshift mutations carry significant consequences for protein functionality, underscoring the critical need to maintain accurate reading frames during transcription and translation processes. Hence the correct option is a and d.