OK, let’s start with a very simple fact: eukaryotic genes have introns. IOWs, they are not continuous. They are made of exons and introns: exon – intron – exon – intron – exon and so on. Exons code for the protein. Introns don’t. So, when the content of the gene is copied to the mRNA, introns must be cut away, and only exons are retained, in order to be translated, so that the mature mRNA can be transferred to the cytoplasm and translated by the ribosome. This process of removing introns is called splicing. Now, a few clarifications: a) Introns exist in prokaryotes too, but they are rather rare. For our purposes, we will only discuss introns in eukaryotes. b) … Continue reading The spliceosome: a molecular machine that defies any non-design explanation.