Final answer:
Nuclear pre-mRNA processing takes place in the nucleus after RNA transcription and before mRNA translation, involving the addition of a 5' cap, 3' poly-A tail, splicing of introns and exons, and sometimes editing.
Step-by-step explanation:
Nuclear pre-mRNA processing occurs after transcription of RNA in eukaryotic cells and before the mRNA is translated into a protein. The pre-mRNA undergoes several processing steps that are essential for creating a stable and functional mRNA molecule capable of being translated by the ribosome. These steps include the addition of a 5' cap and a 3' poly-A tail, which protect the pre-mRNA from degradation and assist in its export from the nucleus. Another crucial step is splicing, where introns are removed and exons are joined together to form a continuous coding sequence. In rare instances, RNA editing may also occur to insert or modify nucleotides within the transcript.