Nonsense mutations yield shortened polypeptides that typically have little or no activity and tend to be highly unstable because of intracellular proteases. Such mutations often display some polarity onto transcriptionally downstream genes. Since frameshift mutations put ribosomes out of the proper reading frame, they often disclose nonsense codons which then result in polarity. They might conceivably affect mRNA stability, attenuation, and, where the gene product is an RNA, mutations might cause a loss of product function or cause improper processing or modification of the product. Large inversions also have the subtle effect of changing gene position with respect to the origin of replication, thus changing the average copy number per cell.
Duplications can have phenotypes when the copy number of that particular region is critical.
They typically cause polarity due to their encoding of RNA termination signals and can occasionally provide new promoters reading into the flanking regions. The frequency of events determines the mode of analysis necessary in order to determine them. Obviously, the above table is a bit deceptive. For example, it has already been stated that some insertion sequences revert at a reasonable frequency and some scarcely revert at all. On the other hand, if an event is occurring at 10 -2 frequency, you may safely assume that it does not involve the occurrence of some very particular base substitution mutation since such events are simply too rare.