MCB 150 Lecture Notes - Lecture 20: Small Nuclear Rna, Ribosomal Rna, Nucleolus

• School: University of Illinois
• Department: Molecular and Cell Biology
• Course: MCB 150
• Professor: Brad Mehrtens

Document Summary

Rrna processing (which does not = splicing) Look at structure of ribos in eu cells. Lots of work goes into putting these together. So all cells have mult copies of their rrna genes. ~280 copies of 5. 8, 18, and 28 s copies. Tandem arrays are groups of subunits that get transcribed together. 5. 8, 18, and 28 s subunit rrna are transcribed by rna pol. 1 into pre-rrna (that contains all of them) Cleavage (or processing) occurs, leaving behind the individual subunits. 5s rrna genes found in a huge array are on x-some 1. Made by rna pol 3 (not 1 like everything else) Nucleolus forms around the arrays of 45s rrna genes. This is called nucleolar organizing regions (nor) Imp: when the nucleolus disappears during m phase, it is because it is not needed to. 3 regions of the nucleolus transcribe rrna because all of the work has been done. Long thin fibers packed into a column.