How a cell edits a gene’s first draft
When a gene is copied, the first RNA version—called pre-messenger RNA—contains both exons, the stretches retained in the message, and introns, the stretches removed during processing. The cell does not send this draft straight to the protein-making machinery. It edits it first.
A molecular machine called the spliceosome recognizes signals near intron boundaries, cuts the RNA, and connects the neighboring exons. The finished messenger RNA can then leave the cell nucleus and be read by ribosomes, which assemble a protein from its sequence. If the cut-and-join step goes wrong, the message may be misread, discarded, or produce an altered protein.
One gene can yield more than one message
The edit is not always identical. Through alternative splicing, a cell can keep different combinations of exons in the finished RNA. That lets the same gene contribute instructions for different protein versions, depending on the cell type or circumstances. In that sense, splicing is not merely cleanup: it is also a way to regulate what a gene produces.
Introns are removed from the RNA message, but that does not mean every intron is biologically pointless. Some contain signals that influence gene activity or how RNA is processed. The practical distinction is that introns do not remain in the usual protein-coding message, while their presence in the original draft can still matter.
