In eukaryotic cells, the majority of RNA is produced inside the nucleus. Several forms of RNA are synthesized there, including messenger RNA, transfer RNA and ribosomal RNA. Two organelles, mitochondria and chloroplasts, contain their own DNA and reproduce autonomously. Both organelles manufacture ribosomes along with messenger and transfer RNA.
Evolutionary biologists think that RNA preceded DNA as genetic material. However, RNA is less chemically stable than DNA. Over millions of years, DNA supplanted RNA as a repository of genetic information. All cellular life forms contain DNA genomes.
Vestiges of this RNA-dependent world survive, however. Many viruses, including influenza and HIV, contain RNA genomes. More importantly, ribosomal RNA catalyzes the formation of peptide bonds during protein synthesis. Protein production would be impossible without RNA to carry out this vital step.