1. After a eukaryotic cell transcribes a protein-coding gene, the RNA transcript, called a pre-mRNA, is processed. The processing takes place in the nucleus, after which the mature mRNA is released into the cytoplasm. Ribosomes in the cytoplasm translate the mRNA into protein. 2. Here we focus on one of several RNA processing steps, called RNA splicing. The pre-mRNAs, just like the genes from which they are transcribed, contain regions that do not code for the translated protein. These noncoding