A celebration of the DNA double helix at 50

2003

YEAR BOOK

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Trinity College Dublin

Kevin Mitchell

A celebration of the DNA double helix at 50

On an April day in 1953, Francis Crick announced to the patrons of the Eagle bar in Cambridge that he had just 'discovered the secret of life'. Fifty years on, this claim does not seem in any way overstated. What Crick and his colleague James Watson had discovered was, of course, the double helical structure of the DNA molecule. This discovery had immediate and profound implications for our understanding of basic biology, heredity and evolution and laid the foundation for the modern field of molecular genetics.

To celebrate the fiftieth anniversary of this momentous discovery, a series of events were held in Trinity College Dublin, hosted by the staff and students of the Smurfit Institute of Genetics. These events included a series of public lectures on various topics in genetics, presented in association with The Irish Times, and culminated with a visit to the College by one of the co-discoverers of the double helix, Dr James Watson, Nobel Laureate. Dr Watson's visit was generously sponsored by and organised in association with Science Foundation Ireland.

Dr James Watson, Professor David McConnell and Dr Onora O'Neill at the lecture 'DNA: 50 Years Ago and Today'.

Dr Watson delivered a fascinating lecture entitled DNA: 50 Years Ago and Today on the 28th April, with the T�naiste, Ms Mary Harney, TD, as guest of honour. We were equally delighted to host Dr Onora O'Neill, Principal of Newnham College, Cambridge, and the author of several philosophical works on bioethics and the societal implications of genetic research, who replied to Dr Watson's lecture. The session was moderated by Professor David McConnell of the TCD Genetics Department.

The lecture was Webcast live around the world, with associated events at many universities around the country. The Webcast was sponsored by a generous grant from BioResearch Ireland, and broadcast via HEAnet. The Webcast stream can be viewed (on a PC) at: http://www.heanet.ie/projects/videoservices/videostreaming/watson%20stream/

Dr Watson gave both a personal history of the work leading up to the groundbreaking discovery and a description of its influence on the development of the field of molecular genetics. At the time that he and Crick, along with a number of other researchers including Maurice Wilkins and Rosalind Franklin, were working to discover the structure of DNA, the following facts were known: Genes had been defined as 'units of heredity' that specified various traits of an organism, passing from one generation to the next and coming together in different combinations. Genes were located on chromosomes, which were made of two types of molecule: proteins and deoxyribonucleic acid, or DNA. The 'genetic material' itself had been shown in 1944 to be composed of DNA; this theory, however, was not widely accepted. DNA seemed far too simple a molecule to fulfil this role, composed of only four types of subunit, A, C, G and T, in roughly equal amounts, with apparently very little potential to store information that could be replicated. It was utterly mysterious how this molecule could be the medium of heredity.

Prof John Hegarty, Provost of Trinity College Dublin, Dr James Watson and Prof David McConnell at the sculpture in Trinity College 'Double Helix' by Brian King, which was commissioned (with a generous gift from Dr. Beate Schuler) to celebrate the anniversary.

With the discovery of the double helical structure of DNA, however, these things suddenly became obvious. The biggest surprise was how simple and elegant the answer was. The genetic information was contained in the sequence of the four subunits along a single strand of the double helix, while the complementary bonding of the bases across the two strands (A on one strand always bound with T on the other, and C with G) immediately showed how each strand could act as a template for the replication of the other. Most importantly, as Dr Watson said, the structure showed that 'heredity follows the known laws of chemistry'. No new rules were needed to explain it. The secret of life lay in the detailed chemical structure of a molecule, a molecule which can now be physically manipulated by the technology known as genetic engineering. This discovery therefore not only had profound philosophical implications but also laid the foundation for the modern field of molecular genetics. This field has progressed in fifty years to the astonishing point where we have been able to 'read our own instruction book', with the final sequence of the human genome (i.e., the order along the chromosomes of the three billion units of A, C, T and G that constitute our genetic makeup), announced on Friday 25th of April of this year.

Dr Watson also presented his views on how the diverse issues arising from potential applications of genetic research should be dealt with by society, with 'common sense' as the guiding principle. In a note that was echoed by the speakers who followed, he emphasised the crucial importance that scientific education will have in enabling individuals and society to make informed choices about the increasing number of genetic issues with which we will all be faced. Dr O'Neill gave a thoughtful response from a philosophical and ethical perspective, sounding a cautionary but optimistic note. Professor McConnell closed the session with a consideration of the impact that the discovery of the DNA double helix has had on genetic research, and an explanation of why it deserves its iconic status as, truly, 'the secret of life'.

This is an edited version of an article which appeared in the 2003-4 edition of the alumni magazine, Trinity Today.

Contact: Dr Kevin Mitchell, Lecturer and SFI Investigator, Department of Genetics, Trinity College, Dublin 2; Tel: +353-1-608-3067; Fax: +353-1-679-8558