3500Ch32-33

3500Ch32-33 - DNA of humans and chimpanzees are 95%...

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Unformatted text preview: DNA of humans and chimpanzees are 95% similar. Nucleic Acids : DNA and RNA • Nucleic acids represent the fourth major class of biomolecules (other major classes of biomolecules are proteins, carbohydrates, lipids) • Genome- the genetic information of an organism DNA Replication Building blocks of DNA Phosphat e 5 Carbon sugar nucleoside Phosphate ester bond Nucleic acids are polynucleotides β-N-glycosidic bond Ribose and Deoxyribose the 5 carbon sugars of DNA Major pyrimidines and purines Seldom found unsubstituted in cells Nucleotides • Nucleotides are phosphorylated derivatives of nucleosides • Ribonucleosides contain three potential hydroxyl groups (2’, 3’ and 5’) • Deoxyribonucleosides can be phosphorylated at the 3’ and 5’ positions • A nucleotide is assumed to be 5’-phosphate unless specified otherwise DNA molecules are very long • Nucleotides have polarity 5’ to 3’ • DNA links to form very long molecules • The E.Coli genome has two chains – each 4.6 million nucleotides. • Human genome 3 billion nucleotides on 24 chromosomes • Structure of B-DNA • Sugar phosphate backbone outside • Hydrophobic bases to the inside • Stacking creates two unequal grooves (major and minor) rise pitch Right handed • Hydrogen bond sites for nucleic acid pairing • Other H-bonds can form with proteins Weak Forces Stabilize the Double Helix (1) Hydrophobic effects . Burying purine and pyrimidine rings in the double helix interior (2) Stacking interactions . Stacked base pairs form van der Waals contacts (3) Hydrogen bonds . Hydrogen bonding between base pairs. (4) Charge-charge interactions . Electrostatic repulsion of negatively charged phosphate groups is decreased by cations (e.g. Mg2+) and cationic proteins Click to edit Master subtitle style Replication is semiconservative! Denaturation of DNA • Double-stranded DNA is thermodynamically more stable than the separated strands (under physiological conditions)...
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This note was uploaded on 02/03/2011 for the course CHEM 3500 taught by Professor Staff during the Spring '08 term at Kennesaw.

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3500Ch32-33 - DNA of humans and chimpanzees are 95%...

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