Posttranscriptional Modification and Processing of RNA

In both prokaryotes and eukaryotes, the primary transcript is considerably larger than the ultimate molecule. 

In both eukaryotic and prokaryotic cells, large precursors to rRNA are transcribed and processed to produce the mature rRNAs. Processing involves methylation of bases and/or ribose and endolytic cleavage to cut out unwanted sequences. The eukaryotic products are the 18, 5.8, and 28 S rRNAs. In prokaryotes, the final products are the 16 S rRNA, a spacer region that includes one or two tRNAs, the 23 S rRNA, and the 5 S rRNA and, in some instances, one or two additional tRNAs. 

Prokaryotic mRNAs function in translation with no processing, whereas a very complex process is used by eukaryotes to produce a mature, functional mRNA. 

Splicing removes 2 additional infrons mature ovalbumin mRNA 

Abnormal mRNA splicing can be one cause of /3+-thalassemia in which the production of /3-hemoglobin chains is greatly reduced. The defect appears to be caused by mutations that interfere with the correct removal of introns from the globin pre-mRNAs. 

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Be able to discuss the posttranscriptional modification and processing of RNAs (rRNA, mRNA, and tRNA). 

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