0How the strands of thread forms a cloth and creates the cloth’s color, shape and designs same way a DNA is responsible for the development and functioning of living organisms.
An organism is made up of cells; cells have Chromosomes; chromosomes has DNA molecules.
Structure of DNA
1. DNA (Deoxyribonucleic Acid) is composed of two Polynucleotide Strands (the polymers of nucleotides). The Nitrogenous Bases in DNA store the instructions for every feature of the entire organism.
2. The two polynucleotide strands run 'antiparallel' to each other i.e., run in opposite directions. The antiparallel strands twist in a complete DNA structure, forming a Double Helix.
Complementary Base Pairings
3. The strands are held together by 'paired' Hydrogen Bonds between the Nitrogenous Bases that are opposite each other. A Purine will only pair with a Pyrimidine, the Adenine Purine will only pair with the Thymine Pyrimidine (A-T) and the Guanine Purine will only pair with the Cytosine Pyrimidine (G-C). These base pairings are termed Complementary Base Pairings.
Reason behind the structure
4. The reason that Purines will only bond with Pyrimidines is that Purines are larger molecules with a double ring structure so in order to ensure that the polynucleotide strands are equally spaced apart, the larger Bases must pair with the smaller bases.
