Splicing is a process of

Removal of Introns : The primary transcripts are very long ;they have molecular weights more than 10 power of 7.Molecular weight of mature mRNA is about 1-2 x 10 power of 6.This means large poion of hnRNA are cleaved off. The primary transcript contains coding regions (exons)interspersed with non-coding regions (introns). These intron sequences are cleaved and the exons are spliced (combined together ) to orm the mature mRNA molecule.This processing is done in the nucleus.Splicing is an energy requiring process. REF :DM VASUDEVAN TEXTBOOK ;7th EDITION ; Page no :591.