What type of RNA undergoes splicing to remove introns?

The process of splicing to remove introns primarily occurs during the maturation of heterogeneous nuclear RNA (hnRNA). hnRNA is the precursor to messenger RNA (mRNA) and contains both exons (the coding regions) and introns (the non-coding regions). During splicing, the introns are removed, and the exons are joined together to form a continuous coding sequence.

This process is crucial for producing a functional mRNA molecule that can be translated into a protein. Once the splicing is complete, the mature mRNA is transported from the nucleus to the cytoplasm for translation. While mRNA does undergo splicing, it is specifically the hnRNA that initially contains introns and is the primary substrate for splicing prior to becoming mRNA.

Therefore, hnRNA is the correct answer because it highlights the stage of RNA that directly undergoes intron removal through splicing before it matures into mRNA.