Final answer:
RNA editing is a post-transcriptional process that changes the base sequence of an RNA molecule. It can regulate gene expression and contribute to protein diversity. This process is considered an ancient mechanism, especially prevalent in mitochondrial RNA.
Step-by-step explanation:
RNA editing is the process where the base sequence of a transcribed RNA can be changed. This is a form of post-transcriptional modification that occurs after an RNA molecule has been transcribed from DNA but before it is translated into a protein. During RNA editing, specific nucleotide bases within the RNA sequence are altered, which can affect the function of the resulting protein. For example, an adenosine base may be converted to inosine (a process common in mammals) or cytidine to uridine. This editing can lead to the creation of different proteins from the same strand of RNA, contributing to protein diversity.
RNA editing differs depending on cellular conditions and may serve as an evolutionary mechanism for regulating gene expression. For instance, in mitochondria, RNA editing is prevalent and is thought to be a relic of an ancient RNA-based regulatory system. Similarly, transfer RNAs (tRNAs) undergo significant post-transcriptional modifications such as base methylation and the enzymatic addition of a C-C-A base triplet at the 3' end, which are critical for their proper function.