MOLECULAR GENETICS 1

Introduction

Inheritance at a molecular level.

DNA is the genetic material for most of the organisms, 

exceptions - viruses -- RNA

DNA -- synthesis of RNA -- protein synthesis -- control traits of individuals.

In this lesson, we will learn how DNA was discovered to be the genetic material, and how this entire process of protein synthesis takes place.

Structure of Nucleic Acids

Nucleic acids are the biomolecules which play a very important role in the process of Inheritance.

Two types of nucleic acids exist: DNA (Deoxyribo Nucleic Acid) and RNA (Ribo Nucleic Acid).

DNA has a double-stranded structure. It is a polynucleotide whose monomer units are deoxyribonucleotide. 

Length of DNA is determined by number of nucleotides in it.

RNA, on the other hand, has a single-stranded structure. It is also a polymer whose monomer units are ribonucleotide.

A nucleotide has 3 components:                     

• Pentose sugar
• Monosaccharide with 5 Carbon atoms
• Ribose sugar in RNA
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• Deoxyribose sugar in DNA
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Nitrogenous base

• Nitrogen containing compound with properties of a base
• 2 types: Purines, Pyrimidines
• Purine
• Heterocyclic aromatic organic compound
• 9-membered ring
• Examples: Adenine, Guanine

Pyrimidine

• Heterocyclic aromatic organic compound
• 6-membered ring
• Examples: Cytosine, Uracil, Thymine

Phosphate group

• Inorganic salt of phosphorus
• Forms backbone of polynucleotide chain along with the sugar

Formation of a polynucleotide takes place using the following linkages:

 

1. Nitrogenous base is linked to the pentose sugar through a N-glycosidic bond to form a nucleoside
2. 
   
3. A phosphate group is linked to 5'-OH of a nucleoside through phosphoester bond to form a nucleotide
4. 
   
5. Multiple nucleotides are joined together through 3'-5' phosphodiester bond to form a polynucleotide
6.