RNA splicing
In eukaryotes the first RNA copy contains introns (non-coding stretches) and exons (coding stretches). Splicing removes the introns and joins the exons. A cap and a poly-A tail are also added.
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Analogy
Editing a film: cutting out scenes and joining the rest.
In practice
Alternative splicing joins the exons in different ways, so one gene can make several different proteins.
Practice
Flashcards
- What are introns and exons?Introns are removed from the RNA. Exons are kept and joined to form the final message.
Interview questions
- Explain how the information in a gene becomes a protein in a eukaryotic cell.
- Transcription in nucleus makes pre-mRNA
- Splicing removes introns, cap and tail added
- mRNA exits to cytoplasm
- Ribosome reads codons with tRNA
- Amino acids joined and folded
Questions people ask
Why do eukaryotic genes have introns?
Introns can allow one gene to produce several proteins by alternative splicing, which greatly increases the variety of proteins. They may also help genes shuffle exons during evolution. Their exact origin is still debated, but many human genes contain several introns.
What do the cap and poly-A tail do?
The 5' cap and the poly-A tail protect mRNA from being broken down, help it leave the nucleus, and help the ribosome recognise and start reading it. Without them, mRNA is destroyed quickly. They are added in the nucleus during processing.