A to D are normal splice donor and acceptor signals. Thalassemias are heritable diseases characterized by sub-normal levels of hemoglobin. Thalassemias that result from changes in splicing signals have been characterized. There are several other examples of mutation of splice donor or acceptor signals leading to use of sequences that don't normally serve as splice donors or acceptors. Other Pages Interpretations Natural mutations in globin genes confirm that the consensus sequences are essential.
Mutations can create, as well as destroy, splice donor and acceptor sites.
Some splicing mutations may have only subtle effects on the protein product, such as the three amino acid deletion resulting from the E to B splice. Its principal activity is the splicing of introns with AU and AC 5' and 3' ends, respectively. Conversely, a small subset of AU-AC introns are spliced by the major spliceosome. Splicing requires transcription by RNA polymerase II .