# During protein synthesis in eukaryotes, what happens during RNA splicing?

##### 1 Answer
Apr 3, 2018

Introns are cut out and exons are joined together.

#### Explanation:

Splicing is a form a regulation that basically says, "are you sure you want this protein?" When a gene is transcribed (into mRNA), it is generally very long. Upwards of 40,000 bases. It is a copy of the coding region and contains regions called 5$UTR (untranslated regions), exons (coding part), introns (noncoding parts), and 3$UTR. This entire thing is called a pre-mRNA.

THe actual mRNA that goes into the ribosome will be much shorter - maybe 4000 bases (size depends on how many amino acids are in the protein). The process of splicing removes the intron sequences (these can be very large), and joins together (or splices together) the exon seqeunces. The codon sequence that codes for the protein is found in the exons.

So the spliceosome represents a level of regulation that splices out introns and connects exons.