Nucleic acid experiment

• The three major components of DNA include a phosphate group, sugar and a base
• DNA is made up of two strands that are held together by hydrogen bonds between complementary bases.
• The DNA is helical in shape, and is stabilized by large numbers of H bonds and the hydrophobic bonding between stacked bases
• The two DNA strands run in antiparallel direction
• Sodium dodecyl sulfate (SDS) is used to purify nucleic acids, as it quickly disrupts the biological membrane inhibiting RNase and DNase activity
• Sodium citrate works with Ethanol in precipitation of the DNA to shield the negative phosphate end of the strand
• EDTA binds the divalent cations, resulting to increased stability. It also prevents the degradation of DNA
• Papain is a cysteine protease from carica papaya
• Papain breaks down proteins as histones are denatured
• The 3 key steps in isolating DNA are homogenization, deproteinization and precipitation
• DNA is insoluble in ethanol
• A buffered system is used to maintain the intracellular and extracellular pH within a very narrow range with resistance to external and internal influences
• Homogenization breaks down sample into smaller pieces for better extraction, which increases the DNA yield
• Homogenization is necessary to release proteins from DNA
• Cold ethanol increases the amount precipitated DNA
• To determine the DNA purity, A260/A280 is used as the formula
• At 280 nm, the absorbance of possible contaminants include tyrosine, tryptophan and cysteine
• Purine and pyrimidine rings have conjugated bonds that have absorption peaks at 260 nm
• The dische test detects the presence of deoxyribose, Murexide test for the purines, wheeler johnson test for pyrimidines, and phosphate test for phosphates