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In addition to the chemical differences we have already talked about here, RNA is also shorter, and generally single-stranded (this does not apply to some viruses as we will see later). RNA also functions differently from DNA. While the only role of DNA is the storage of genetic information, RNA has many different roles to fulfil. There are several types of RNA which perform these different functions. Ribosomal RNA (rRNA) form complexes with protein to form ribosomes, the site of protein synthesis wihtin the cytoplasm of the cell. Messenger RNA (mRNA) carries the information recorded in DNA from the nucleus to the cytoplasm of the cell. Small nuclear RNA (snRNA) is involved in pre-mRNA splicing. Heterogenous nuclear RNA (hnRNA) is the primary transcript from the eukaryotic enzyme, RNA polymerase II. hnRNA is the precursor of all mRNA often called "pre-mRNA", prior to the removal of introns. Small nucleolar RNA (snoRNA) is found in the cell's nucleolus where it processes and methylates rRNA. |
