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Lecture 21

Biology 1202B Lecture Notes - Lecture 21: Chromosome, Transfer Rna, Peptide

Course Code
BIOL 1202B
Patrick Mc Donald

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RNA World and RNA
Before DNA RNA World
-DNA RNA Protein
>Complex process how did it arise?
-RNA world hypothesis
>RNA stored genetic information
>RNA catalyzed chemical reactions (ribozyme)
>Served DNA and protein like functions
Before DNA RNA World
>Later in evolutionary time
-DNA took over as hereditary material
-Proteins became the major catalysts for reactions
>Building blocks of the cell
-Transition not entirely complete
>RNA still catalyzes several fundamental reactions
Before DNA RNA world
-Life requires the ability to catalyze reactions that lead, directly or indirectly to the production of
more molecules like themselves
-RNA has the unique potential to act as both information carrier and catalyst
>Assembly of RNA polymers in the RNA world is random
-Function will depend on sequence = structure
-The property of RNA molecules that allow it to be a catalyst for ribozymes is its ability to fold
into shapes
-single stranded RNA can hold into many different structure. Like protein, structure determines
catalytic activity
RNA World Experiments
>Generate large pool of random DNA and transcribe
>RNA molecules which have specific biochemical properties isolated
-These properties include catalyzing a variety of reactions
>Main difference between protein enzymes and ribozymes is reaction speed NOT diversity of
RNAs can have alternate conformations (like proteins)
-alternate conformations have different biochemical properties
-random assembly of nucleotides is able to produce a functional ribozyme
Alternate conformations have different biochemical properties
-1 ribozyme with 2 functions
>Structure determines function
Certain catalytic activities would be important
-An RNA which can catalyze templated polymerization would be important
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