AS.020.331 Lecture Notes - Lecture 7: Rna-Dependent Rna Polymerase, Catalysis, Messenger Rna
Document Summary
Rna stores sequence information and does catalytic actions. Single stranded rna molecules, when denatured, act as templates for replication (specific catalysis) Single stranded rna molecules form stable, sequence-dependent secondary structure with other catalytic functions: ribozymes. Rna molecules serve as both gene and gene product: rna/ protein-life. Proteins are specifically tailored for chemical catalysis. A new role for messenger rna is the storage of protein sequence information. Proteins can assist in translation and replication: key protein: rna- dependent rna polymerase. This protein eliminates the need for ribozyme assistance: mixed life. Disadvantages of rna genes: chemical instability of ribose sugar compared to deoxyribose sugar, spontaneous deamination from cytosine to uracil- unstable bases are not favorable, differential stability of a-u and g-c makes sequence dependent conformers unavoidable. G-c pair is stronger than a-u pair. Regular double stranded rna helices are very rare. Dna fixes these problems: there is alkaline stability in the deoxyribose sugar.
