Nucleic Acid : DNA and RNA (PART -1)

 Nucleic acid is biopolymer,essensial for all living beings. They were first reported by Friedrich Miescher (1871) in nuclei of pus cell. He named them nucleic.They can be found in both nucleus and cytoplasm .Altman renamed nuclein and called them Nucleic acid.

Nucleoprotein 

• Nucleic acid along with basic proteins make nucleoprotein which is sub unit of chromosome. 
•  In nucleoprotein, nucleic acid is prosthetic group and protein part consist of protamine and histone (basic nature). 
• They are very complex and high molecular proteins. 

Composition 

Basic structure of nucleic acid consist of Sugar, nitrogenous base *(adenine,guanine,thymine,cytosine,uracil) and phosphorus. This combined structure of sugar, phosphorus and nitrogenous base is known as nucleotide.

•  DNA is made up of deoxyribonucleotides which is further made up of Deoxyribose sugar, phosphorus, and nitrogenenous bases (adenine,thymine guanine, cytosine)
• RNA is made up of ribonucleotides which is further composed of Ribose sugar,phosphorus, nitrogeneous bases (adenine, uracil, guanine, cytosine) 

These two nucleic acid are recognized or differentiated on the basis of pentose sugar and nitrogeneous base .

Functions of nucleic acid 

In  nucleic acid is associated with formation of cytoplasm ,division of cell and also to carry hereditary character (genes). 

In Cytoplasm  it is associated with formatation of proteins.

Isolation of nucleic acid 

1. Firstly nucleoprotein are extracted from minced tissue with NaCl solution. 
2. After that, in presence of proteolytic enzyme like trypsin, proteins is separated by saturating with NaCl or mild acid or alkali hydrolysis. 
3. During this process proteins get precipitated and can remove easily. 
4. Nucleic acid is precipitated with alcohol.
   
   
    

Separation of DNA and RNA 

1. Isolation of DNA 

There are several ways for extraction of DNA from nucleic acid. 

• By removing RNA by treating with phenol, as RNA is soluble in phenol. 
• By degradation of RNA into soluble fragments by treating nucleic acid with  (RNA digesting enzyme) 
• By degradation of DNA with deoxyribonuclease.

Native DNA consist of extremely long helical coil, to precipate it into long fibrous form, ethyl alcohol is added into DNA solution. This can be removed by winding the fibrous material around the stirring rod. 

2.Isolation of RNA 

A heterogeneous mixture of tRNA,mRNA,rRNA and degraded RNA is obtain. For isolation of RNA following ways can be used 

• Column chromatography of this mixture on the columns of methylated albumin coated on kiselguhr (MAK column) 
• Gradient Centrifugation  in sucrose solution 
• Ion exchange chromatography 

Biological importance of nucleic acid 

1. They carry hereditary character from one progeny to another 
2. They are associated with protein synthesis in cytoplasm.

*Nitrigenous base

They are of two types 

1.Purines 2.Pyrimidines

• Purines :Dicyclin in nature . Adenine and guanine 
• Pyrimidines:Monocyclic in nature. Thymime, cytosine, uracil. 

Nucleotide vs nucleosides