BCHM 4116 1st Edition Lecture 2 Outline of Last Lecture I. Biochemistry 4116 OverviewII. The Central Dogma/ Challenging the Central Dogma Outline of Current Lecture III. Structural basis of genetic material: Nucleic acidsA. DNA vs. RNAIV. Purine and Pyrimidine Basesa. Keto-enol tautomeric shifts V. DNA better suited as genetic material Current LectureStructural Basis of Genetic MaterialDNA vs. RNADNA1. Four bases make up DNA: a. A  adenine b. T  thymine c. C  cytosine d. G  guanine 2. ‘deoxy’ --- DNA doesn’t have a hydroxyl group (OH) at the 2’ position on the sugar3. DNA is a polymer of nucleotides linked together by phosphodiester bonds 4. Double strandedRNA1. Four bases make up RNAa. A  adenine b. U  uracil ( U replaces T in RNA)c. C  cytosine These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.d. G  guanine e. RNA has a hydroxyl (OH) on the 2’ position on the sugar f. RNA is a polymer of nucleotides linked together by phosphodiester bonds g. Single stranded Purine and Pyrimidine Bases Purines1. 5-member imidazole ring, fused with a pyrimidine (aromatic) 2. There are 2 purines a. Adenine (A) b. Guanine (G)Pyrimidine1. 6-member aromatic ring2. There are 3 pyrimidinesa. Cytosine (C)b. Uracil (U)c. Thymine (T) 3. The two nitrogen’s in a pyrimidine are separated by a carbonyl Keto-Enol Tautomeric shiftsBases can undergo keto  enol tautomeric shifts. Keto: double bond linking the oxygen to carbonEnol: alcohol group connected to carbon This shift results in the bases ability to hydrogen bond.Quantifying Nucleic Acids: Measure absorbance at 260 nm (UV light) due to their aromaticity Putting it together:Both DNA and RNA molecules are made up of a sugar and a base. A sugar and base are linked together by a N-glycosidic bond. The 1’ position on a sugar is linked to a nitrogen atom on a base (purine/pyrimidine). A sugar and based, connected through an N-glycosidic bond, is called a nucleoside. Two nucleosides (sugar + base) are joined together through a phosphodiester bond. Notice thatit is a ‘di-ester’ bond. This linkage results in two esters forming at the 5’ and 3’ positions of the sugar. When a phosphate group is added to a nucleoside, it is called a nucleotide. A nucleotide is a nucleoside plus a phosphate group. Hence, DNA and RNA molecules are polymers of nucleotides. DNA and RNA is always read from the 5’  3’, unless otherwise stated. Why is DNA better suited as genetic material?1. DNA lacks a 2’ OH (hydroxyl). This means that DNA can’t be readily hydrolyzed, resulting in greater stability when compared to RNA. 2. DNA contains thymine instead of uracil ( cytosine to uracil reaction)a. At very low concentrations in DNA, cytosine is deaminated, resulting in the formation of uracil. When DNA ‘sees’ uracil, it knows that there should actually be a cytosine there. This is then fixed, so that any uracil on a DNA molecule is converted back to