Explain the Watson and Crick model of DNA.

Explanation

Watson and Crick model of DNA:
DNA molecules consists of two polynucleotide chains.
These chains form a double helix, Structure, with two strands, which run anti-parallel to ne another.
Nitrogenous bases in the centre are linked to sugar-phosphate units, which form the back bone of the DNA.
Pairing between the nitrogenous bases is very specific and is always between purine and pyrimidine linked by hydrogen bonds.
Adenine [A] links Thymine [T] with two hydrogen bonds `(A=T)`
Cytosine [C] links Guanine [G] with three hydrogen bonds `(C-=G)`. This is called complementary base pairing.
Hydrogen bonds between the nitrogenous bases make the DNA molecule stable.
Each turn of the double helix is `34A^(@)` (3.4 nm). There are ten base pairs in a complete turn.
Nucleotides in a helix are joined together by phosphodiester bonds.