Nucleic Acids Nucleic acids are: Polymeric macromolecules. Have high molecular weight. Made from monomers known as nucleotides. There function is encoding, transmitting and expressing genetic information. Why did they called Nucleic Acids ? Because they where found inside the nucleus. Nucleic Acid Components DNA, RNA Nucleotides Phosphate group Nucleoside Sugar Deoxyribose (DNA) Ribose(RNA) Nitrogen Base Pyrimidine CTU Burien A G Esters of phosphoric acid What are the other functions of Nitrogen bases in the cell ? Physical and Chemical Properties 1- Absorption of Ultra Violet rays (UV): Nucleic Acids give high absorption of UV rays at Wave length (260) because of Nitrogen and double ponds. This is one method used to figure the concentration of DNA in solution. This occurs because the hydrogen bonds between the bases change their light absorbing properties. The absorbance at 260nm will increase about 30% when DNA is denatured. Hypochromic effect (Hypochromism): Hypochromism refers to the fact that DNA has a lower absorbance at 260 nm than the absorbance of the monomers Nucleotides. 2- Melting Temperature: IS The temperature in which half the DNA molecules are denatures (80-90)C. *After cooling the DNA double strand rebind ( Annealing or renaturation). The UV absorption suddenly increase The viscosity decreases. And this called ( Hyper chromatic effect). This property is used to estimate the G-C content of a DNA molecule. The high concentration of G-C bonds gives high absorption of UV light Why ? DNA denaturation is the conversion of the double stranded DNA into two single stranded molecules. 3- Solubility Hydrophobic Soluble in salt solutions 4- Viscosity : DNA is more viscous than RNA ( Hydrogen bonds) RNA is more soluble in aqueous solutions then DNA because of the Hydroxyl group of the ribose sugar. 5- pH effect : pH Decrease < 4 pH Increase > 11 * Degradation of Hydrogen bonds Degradation of Hydrogen bonds and separation of Nitrogen bases Reverse Non - Reverse RNA decomposes at pH 12 DNA decomposes at pH 9, 100 C DNA, RNA separation: Centrifuge Agarose gel electrophoresis