Final answer:
Three of the four rRNA genes are transcribed as a single precursor by RNA Polymerase I, which includes the 5.8S, 18S, and 28S rRNAs. The 5S rRNA gene is separately transcribed by RNA Polymerase III.
Step-by-step explanation:
Three of the four rRNA genes are transcribed as a single precursor by RNA Polymerase I. In most eukaryotes, this includes a 45S precursor rRNA that contains the 5.8S rRNA, 18S rRNA, and 28S rRNA. These are then processed into their mature forms. The transcription of the 45S precursor rRNA involves an upstream promoter to which RNA Polymerase I binds along with transcription initiation factors. However, the 5S rRNA gene, being the exception, is transcribed by RNA Polymerase III, from promoters located within the transcribed sequence itself, and its gene copies may be distributed on multiple chromosomes.