Exp7a

            Hydrolysis of nucleic acids would have different effects on RNA or DNA depending on the acidity or alkalinity of the reagent used. Acidic hydrolysis of DNA with 1 mM Hleads to the removal of its purine basics by cleavage of the purine glycosicle bonds, but on the other hand RNA would virtually unreactable. In the DNA acid hydrolysis, the glycosiaic bond between pyrimidine bases and 2'- deoxyribose is unaffected, and the sugar-phosphate backbone is maintained. The purine-free polynucleotic product is called apurinic acid.

            While DNA is affected by acid hydrolysis, it is not susceptible to alkaline hydrolysis. But RNA is alkali labile and hydrolyzed by NaOH. There is a random cleavage in RNA and the ultimate products are mixtures of nucleoside 2' - and 3' monophosphates.  Abstraction of the 2'-OH hydrogen by hydroxyl anion leaves a 2'-OH that carries out a nucleophilic attack on the sigma phosphorus atom of the phosphate moiety, resulting in cleavage of the 5'-phosphodiester bond and formation of a cyclic 2', 3'-phosphate. This cyclic 2', 3'-phosphodiester is unstable and decomposes randomly to either a 2'- or 3'-phosphate ester. DNA has no 2'-OH, therefore DNA is alkali stable.
 

Exp7b

             Extraction of DNA is a relatively very simple procedure; especially in tissues with a high nuclear to cytoplasmic mass ratio. These tissues can be found in parts of the body such as the thymus and the spleen. The experiment employs the homogenization of the sample in isotonic saline solution. This part of the procedure is needed to be buffered with Na-citrate at pH 7.4. This will enable the DNA protein complex to precipitate. Ca and Mg is chelated by the Sodium Citrate, that would inactivate the enzyme. It is then followed by the dissolution of the precipitate with 2M NaCl. A fibrous white precipitate is then re-precipitated with 95% ETOH to purify the DNA, Sevag extraction is then employed.
 

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Human Genome Project and Bioinformatics
Chemistry 145.1
Experiment No. 1
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Experiment No. 3
Experiment No. 4
Experiment No. 5
Experiment No. 6
Experiment No. 7
Experiment No. 8
Experiment No. 9
Experiment No. 10
Experiment No. 11
Experiment No. 12
References