Discovering the secret of life

On February 28, 1953, Cambridge University scientists James D. Watson and Francis H.C. Crick announced that they had determined the structure of DNA. 63 years on, it remains a huge milestone in the history of science.

Plaque outside the Eagle pub, where Watson and Crick announced their discovery.

In his best-selling book, The Double Helix (1968), James D. Watson describes one particular instant from February 28, 1953. He recalls how he, a 25-year-old American bacteriologist and Francis H.C. Crick, a 37-year-old British physicist, had walked into the Eagle Pub before Crick had made his announcement - “We have discovered the secret of life!”

In case you are under the impression that they might have already had one drink too many, you can’t be further away from the truth. For earlier that morning, they had worked out the double helix structure of deoxyribonucleic acid, popularly known as DNA.

Know it? Or know it! While three of those involved in determining the double-helix structure of DNA were awarded the Nobel Prize for Medicine or Physiology in 1962, F failed to share the honour. This is because F died of ovarian cancer in 1958 and the Prize rules prevent it from being awarded posthumously. Who is F? Send your answers to ganesh.a.s@thehindu.co.in with your details. [subject: DNA] Last week’s answer Vectograph (V) is a picture that gives three-dimensional effect when viewed through polarising spectacles. Marielle Catherine George of Class VII, Crescent Castle Public School, Ooty, was among those who got it correct. Congratulations!

Watson and Crick were just two of many scientists who were simultaneously working on figuring out the structure of DNA. Their approach involved working with three-dimensional models to reconstruct the DNA molecule.

Not far from Cambridge University, Rosalind Franklin employed X-ray crystallography to study DNA at King’s College. She was successful in obtaining an X-ray diffraction pattern from a sample that showed a helical shape or cross. Without her knowledge, Maurice Wilkins, one of her colleagues, showed the image to Watson.

The double helical model that Watson and Crick were developing was thus experimentally confirmed using Franklin’s picture. By March, they fine-tuned their model and in the April 25, 1953 issue of Nature, published their historic “A Structure for Deoxyribose Nucleic Acid”.

  Watson and Crick came up with a double helical structure in which the two ribbons of phosphate-sugar are held together by a pair of bases. The two ribbons can be compared with the handrails of a spiralling staircase and the pair of bases would then constitute the stairs.

Suggesting a physical structure for the DNA turned out to be a big first step towards genetic studies of the future. In their paper, they had noted that “It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material” - establishing therein that the proposed double helical structure laid the physical basis for encoding and transmission of genes for the first time.

While Watson and Crick shared the Nobel Prize for Medicine or Physiology in 1962 with Wilkins, Franklin’s death in 1958 meant that she was ineligible for it. The decades that followed reshaped biology and medicine, with genetic engineering, rapid gene sequencing and many other techniques that form the building blocks of the biotechnology industry, stemming out as a consequence. In fact, the double helix structure has gone on to become a cultural icon, finding its way into art and architecture.