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Lecture 10

BIO SCI 99 Lecture Notes - Lecture 10: Polynucleotide, Peptidyl Transferase, Nucleoside

Biological Sciences
Course Code
Olga Razorenova

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Week 1:
Central Dogma-
DNA → RNA → Protein
DNA is in nucleus, proteins are made in cytoplasm.
DNA is a template for its own synthesis
RNA Polymerase: opens DNA and makes RNA from template strand.
This is transcription. RNApol is a protein.
rRNA: ribosomal most abundant
tRNA: amino acids are attached to it
Functional RNA: (tRNA and rRNA) make 95% of RNA in cell.
Exceptions: RNA can replicatself. RNA → DNA (reverse transcription & telomerase). Protein
exception- Prions: mad cow disease. Turns alpha helix into beta sheets. (changes protein
structure). Protein affecting protein.
Peptidyl transferase
Structure of DNA & RNA-
Nucleoside = base + sugar.
Glycosidic bond: covalent joining of base to C in sugar, dehydration
Phosphate covalently bonds to 5’C on sugar to form nucleotide
Nucleotide = base + pentose sugar + phosphate group
5’ = phosphate, 3’ = sugar
Purine(planar with small pucker): A&G, Pyrimidine(planar): C&T/U
Phosphodiester bond: 5’phosphate group of one nucleotide connects to 3’
hydroxyl group of the next.
Residues: joined nucleotides
Oligonucleotide: <50 bases. Longer = polynucleotide.
Bases have alternating double bonds
Hydrophobic stacking: minimizes contact w water and keeps stable 3D structure
Base pairing: H bond between amino and carbonyl groups
Minor bases occur that affect structure and function.
Polarity of DNA/RNA: due to free 5’ and 3’ ends.
Backbone is hydrophilic
RNA has OH on sugar and DNA has H.
RNA is more susceptible to hydrolysis.
Proteins- made of amino acids
2 AA = peptide, more = polypeptide
Chargaff’s rules: base composition varies in species, different tissues from same species
have same composition, base composition doesn’t change in given species, A+G=T+C.
Major & Minor grooves exist. One turn is 10.5 base pairs (34A).
Franklin “photograph 51” x ray diffraction = double helical structure. Watson & Crick’s
wire model of winding DNA structure.
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