10 Salient Features of DNA Double Helix Model of Watson and Crick (1953)

The 3 dimensional model of DNA proposed by J.D Watson and  F.H.C Crick is called B DNA; the most common form of DNA
  • Laboratory: Cavendish laboratory
  • Other major contributors: Maurice Wilkins and Rosalind Franklin of Kings College, London provided the x-ray crystallographic data.from that data Watson and crick got the idea of DNA double helix
  • Phobeus Levene proposed the Tetra nucleotide theory and Linus Pauling's triple helix model. Both these even though wrong provided many clues regarding the DNA structure
  • Erwin Chargaff of Columbia University proposed the complementarity of base pairing. Watson and Crick applied this for orienting base pairs within DNA double helix and proposes a DNa copying mechanism based on this data.

10 Salient Features of DNA double helix model

10 Salient Features of DNA double helix model

1.   DNA is made up of two strands that are twisted around each other to form a right-handed helix, called a double helix.

2.   The 2 strands are anti-parallel; one strand has 3′ C of sugar woth –OH in the “upward” position, and the other strand has 5′ C with P in the upward position

3.   Each strand is made up of deoxyribonucleotides joined by phosphodiester bond

4.   Sugar and Phosphate forms the backbone of DNA strand

5.   The two strands are held together by hydrogen bonds between nitrogenous bases

6.   Base Complementarity Relationship (Chargaff’s Rule)

Adenine pairs with Thymine by 2 H bonds

Guanine pairs with Cytosine by 3 H bonds

See more Chargaffs Experiment and Chargaffs Rule


7.   DNA contain 2 grooves, called the major groove and the minor groove. Major groove is wide and deep and minor groove is narrow and shallow.

major groove and the minor groove DNA
These grooves arise because the glycosidic bonds of a base pair are not diametrically opposite each other 

DNA Dimensions

DNA Dimensions B DNA Watson and Crick model

8.   The diameter of the double helix is 2 nm (20 A0)

9.   Distance btw adjacent base pairs is 0.34 nm (3.4 A0)

10.                There are ~10 nucleotide base pairs per turn of helix

1 turn=0.34x10=3.4 nm (34 A0)

This is a summarized video on DNA Double Helix Model of Watson and Crick

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