Answer Bank Splicing occurs while the mRNA is attached to the spliceosome. Small RNAs in the spliceosome recognize the
5^(')
and
3^(')
splice site sequences. In splicing, exon sequences are removed from the mRNA in the form of lariats and are degraded. Splicing occurs after the mRNA enters the cytoplasm but before it binds to the ribosome. One mRNA can sometimes code for nsinge than one protein by splicing at alternative sites.