If x 5 2 x 3 , evaluate x2 x.
Chapter 24: Nucleic Acid Structure 4-‐7-‐16 Central Dogma: DNA to RNA to Protein Nucleotides are composed of nitrogenous base, a sugar, and a phosphate group Nucleoside: nitrogenous base and sugar only Pyrimidine bases: -‐ Cytosine, uracil, and thymine Purine Bases: -‐ Adenosine, and guanine Tautomerization: -‐ Uracil has possible lactam and lactim forms -‐ Guanine has possible keto and enol forms Functions Polynucleotides: -‐ building blocks of DNA and RNA mononucleotides: -‐ most have ribose with a phos group on C5 -‐ regulators of metabolism (cAMP and cGMP) -‐ source of energy -‐ ATP is used for most metabolic processes -‐ GTP is used in protein synthesis -‐ Only phosphate groups transmit energy -‐ Base portion is signaling part DNA Chargaffs rule: adenine and thymine are 1:1 ration, cytosine and guanine are 1:1 ratio Structure: -‐ two strands are anti parallel -‐ backbone is alternating ribose and phosphates -‐ inside is base pairs -‐ 3 possible conformations: A, B, and Z -‐ B is the most common conformation -‐ Z is the only left handed conformation and relevance is unknown Torodial DNA: -‐ negatively charged supercoiled DNA Palindrones: -‐ inverted repeats in DNA sequence; they cause the cruciform tertiary structure Topoisomerases: -‐ they control supercoiling -‐ Type 1 breaks one strand of DNA -‐ Type 2 breaks both strands
