Summary
The removal of introns and joining of exons by the spliceosome to produce mature mRNA.
In depth
The spliceosome (snRNPs plus proteins) recognises a 5' GU donor site, a branch point A and a 3' AG acceptor site. Two transesterification reactions cut out the intron as a lariat and join exons.
Splicing errors cause diseases such as some forms of beta-thalassaemia.
Introns can be much longer than exons (the average human exon is about 150 bases and intron several thousand), so the spliceosome must find exons within a sea of introns, aided by exonic splicing enhancers and SR proteins. Group I and II introns are self-splicing RNA enzymes and are found in organelles and bacteria. Introns may encode regulatory RNAs.
Mutations in splice sites cause about 10 percent of disease-causing point mutations. Antisense drugs, such as nusinersen for spinal muscular atrophy, correct splicing by changing exon inclusion.
Key idea: Sharp and Roberts discovered split genes in 1977 and received the 1993 Nobel Prize, upsetting the earlier view that genes are continuous.
Frequently asked questions
What is Splicing?
The removal of introns and joining of exons by the spliceosome to produce mature mRNA.
Which area of biology covers Splicing, and how advanced is it?
Splicing is one of the 52 topics in Molecular Biology. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include RNA Processing, Alternative Splicing, Nonsense-Mediated Decay.
Can you give an example of Splicing?
The dystrophin gene has 79 exons joined into one mRNA.
What should I learn before Splicing?
Work through the Beginner topics in Molecular Biology first, such as Central Dogma, DNA Replication, Base Pairing, then return to Splicing. Intermediate topics assume the Beginner vocabulary.
What topics are related to Splicing?
The closest topics to Splicing are RNA Processing, Alternative Splicing, Nonsense-Mediated Decay, Transfer RNA. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Splicing?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Splicing. To practise the whole of Molecular Biology, use the Molecular Biology quiz.
How is Splicing different from RNA Processing?
Splicing: The removal of introns and joining of exons by the spliceosome to produce mature mRNA. RNA Processing: In eukaryotes, pre-mRNA gets a 5 prime cap, a poly-A tail and has introns spliced out. Read both side by side and note what each one explains.
How should I study Splicing step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with RNA Processing and explain the difference aloud. Finally, take the Molecular Biology quiz and come back to this page for any question you miss.