Double Helix model of DNA: The double helix describes the appearance of double-stranded DNA, which is composed of two linear strands that run opposite to each other, or anti-parallel, and twist together. Each DNA strand within the double helix is a long, linear molecule made of smaller units called nucleotides that form a chain.

Who proposed Double Helix model of DNA?

James Watson and Francis Crick pioneered in 1953 to put forward the molecular structure of DNA which they termed the “double helix” in a journal. In 1962, Watson and Crick along with Maurice Wilkins (their colleague) were even awarded the Nobel Prize for this breakthrough in the history of medicine.

Watson-Crick Structure of DNA

They discovered the double helix structure of DNA and proposed on X-Ray diffraction pattern.

Important features of this model was:

• Complementary base pairing between two strands of polynucleotide chains.
• Data for this pattern was produced by Maurice Wilkins and Rosalind Franklin.

Chargaff’s rule

• It states that the amount of guanine should be equal to cytosine and the amount of adenine should be equal to thymine.

[A] = [T]  [G] = [C]

• Adenine with Thymine and Guanine with Cytosine are always joined by hydrogen bonds.
• The ratio of Adenine and Guanine to that of Thymine and Cytosine is always equal to one.

[A + G] / [T + C] = 1

Central Dogma

Francis Crick proposed the Central Dogma of molecular biology which states the genetic information flows from DNA to MRNA (transcription) and then from MRNA to proteins (translation) this is unidirectional process. Central Dogma is bidirectional in some viruses and this process is called reverse transcription.

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By Team Learning Mantras