Lecture 6b - BIO 311 RNA Structure and Function Central...

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Unformatted text preview: BIO 311 RNA Structure and Function Central Dogma RNA is the intermediate between DNA and Protein Several Types of RNA Messenger RNA (mRNA): Carries the genetic information out of the nucleus into cytoplasm for protein synthesis. Transfer RNA (tRNA): Brings the amino acid to the ribosome and d ecodes the information in mRNA. Ribosomal RNA (rRNA): Makes up ribosome , constitutes 50% of a ribosome, which is a molecular assembly involved in protein synthesis. Small Nuclear RNA (snRNA): The snRNAs have various roles in the processing of the other classes of RNA. Catalytic RNAs (cRNA): Catalyses many reactions in the cytoplasm of the cell. Interfering RNAs (siRNA, RNAi, antisense RNA, microRNAs) There are 100s of small RNAs that interfere with gene expression. Interesting Facts about RNA Approximately, 5-10% of total weight of a cell is RNA (compare with only about 1% DNA!). The extra hydroxyl group in RNA makes it more susceptible to damage by hydrolysis; that's why DNA is a more stable repository of genetic information. RNA is the genetic material in some viruses (which don't have DNA). RNA is found in the nucleus and in the cytoplasm but DNA is found only in nucleus. DNA can be replicated, but only when assisted or catalyzed by proteins (enzymes) but RNA is capable of both self replication and catalysis. THE RNA WORLD • RNA can carry genetic information like DNA • RNA can be enzymatic like protein Secondary Structure of DNA What is RNA? RNA is a Long Polymer of Nucleic Acid • Ribose (a pentose = sugar with 5 carbons) • Phosphoric acid • OH- on the 2’ carbon • Uracil instead of Thymidine • Organic bases ; Pyrimidines – C ytosine and U racil Purines – A denine and G uanine library.thinkquest.org/.../ RNA.htm RNA’s primary structure is related to DNA Double-Stranded Single-Stranded RNA has intra-strand base pairing 5’ 3’ Single-stranded does not mean without structure. Non-Watson Crick Base Pairs Phylogenic studies revealed base pairing other than A-U and G-C in RNA Biochemical studies confirmed these observations A-A C-A U-U A-G G-G C-U U-G Wobble U-G Reverse Wobble Secondary Structures in RNA Tertiary Structures in RNA rna.urmc.rochester.edu/ john/ RNA Tertiary Structures Are Reminiscent to those Found in Proteins RNA function is dependent on RNA structure Differences between DNA and RNA Characteristics Characters DNA RNA 1. Molecule Double stranded, helical Single stranded, with variously folds and twists. 2. Pentose sugar Deoxyribose Ribose 3. Pyrimidine base Thymine Uracil 4. Complementary base pairing Always present and exists between A = T and G = C (Watson/Crick BP) Intra-strand base pairing present in twisted segments Pairing is between A = U and G = C and other 5. Ratio of Purines: Pyrimidines Always 1:1 Not necessarily 1:1 6. Polymerase DNA polymerase needs a primer RNA polymerase does not need a primer Telomeres are Repeated Sequences at the Ends of Chromosomes End Replication Problem:...
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Lecture 6b - BIO 311 RNA Structure and Function Central...

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