BIOB11H3 Lecture Notes - Lecture 4: Ribosomal Rna, Transfer Rna, Isotopic Labeling
Document Summary
The reason that they have an arrowhead type shape to them is because of the organization of the rrna genes-one after another and the fact that they are being actively transcribed by multiple rna polymerases. The part where the dna is pointed to is a double thick line, whereas the smaller lines that form the arrowhead seem to be single thick. The individual strands of the arrowhead are individual strands of the rna molecules. The ones at the point of the arrow is where rna polymerase molecules have just started (chain is about 5-10 nucleotides long) After a while the rna polymerase will move down to the end of the template, making it about 1000 transcripts long. When it is about finished with the transcript, it is about 2000 nucleotides long. Most eukaryotes: rrna gene clusters (nors) exist as 300-400 tandem repeats on several chromosomes. Rna size can be estimated based on sedimentation of the molecule during centrifugation.
