(rRNA) A form of * RNA that is confined entirely to the *ribosomes. Synthesis of rRNA takes place on distinctive parts of the chromosomes associated with the nucleolus, called * nucleolar organizers. The base composition of rRNA is very similar in all species. After synthesis it combines with protein to form nucleoprotein. The partly constructed ribosomes then leave the nucleus, via nuclear pores, and enter the cytoplasm where synthesis is completed. The absence of fully constructed ribosomes in the nucleus may account for the absence of protein synthesis there. Compare messenger RNA , transfer RNA. |
