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Nucleic acids are built up from nucleotides as building blocks Lecture 1a Lehninger Principles of Biochemistry Chapter 8 sections 1 &2 Nucleotides and Nucleic Acids Copyright © 2004 by Worth Publishers Know the molecular structure of a nucleotide Know the general structural differences between pyrimidine and purine bases. Know the numbering system. The pentose is attached at which N? Ribose or deoxyribose? 1 Know the structure of adenine. Differentiate it from guanine. Only β-D-ribofuranose is present in RNA and DNA Recognize the various pyrimidines. It takes one reaction to convert C to U but 2 rxns to go from C to T Variability in C2 and C3. The rest are planar. 2 Distinguish between nucleotides and nucleosides. Know abbreviations and terms used. 3 RNA and DNA share: adenosine, cytidine, guanidine. RNA uses uracil while DNA uses thymidine 4 Note: both DNA and RNA strands have a “polarity”. Direction is: 5’ -> 3’ ends. Note: phosphodiester linkage. What’s main structural difference between RNA and DNA? 5 Tautomers of Uracil: Lactam is most common form The base rings absorb UV radiation. Most other biomolecules do not. (aromatic side chains of amino acids do). Changes in absorbance at these λ’s can be used to monitor state of DNA. Abbreviated way to write a deoxyribonucleic acid strand with sequence 5’-ACGTA-3’ DNA double helix (Watson-Crick; B-DNA). Note the dimensions. 6 Historic expts: Avery, Mcleod, McCarty Experiment. Understand what it shows. 7 Hershey-Chase Experiment Understand what it shows and why. 8 X-ray diffraction data by Rosalind Franklin from DNA fibers suggested helical structure. Know the dimensions and general structural properties. Implications. 9 Complementary DNA double strand (double helix) follows Watson-Crick rules: A=T and G-=C Strands are antiparallel. 10