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Monday, April 8, 2013

DNA 60 years on Date: 23 March 2013

Sent in by Zita. Guidance on formatting from Speedy is gratefully acknowledged.

DNA 60 years on     Date: 23 March 2013

A transcript (or as close as possible) of a programme on BBC Radio 4 by Prof. Robert Winston on the 60th anniversary of the discovery of the double helical structure of DNA by Francis Crick and James Watson in Cambridge, England. (This was intended for a general audience)



60 years ago no one had hardly heard the 3 letters DNA but it’s now everywhere; finding of Richard III in a car park, rogue horse meat in food, identifying a murderer and in medicine, the promise of new treatments for disease. From health to crime, from disease to unique fingerprint for each person, the story of DNA gathers momentum.

On February 21st 1953 Crick and Watson worked out the structure of DNA and it was published as a single page article in the scientific journal, Nature on April 25th 1953.

Francis Crick had started his career 25 years prior to that as a biologist while he reminisced in a cowshed about how a calf is produced. He realised that one sperm out of several millions fertilized one egg to form a one celled zygote which repeatedly divided into 2 and 4 and so on and each cell that resulted must have a carbon copy of the genetic material in the sperm. Where is this material stored in the minute sperm head? And how is it copied? Answers to these two questions seemed to him to be key. He knew that it had to be written in a chemical language.  Crick was in University of Cambridge’s prestigious laboratory in 1951 when he was joined by 23 years old James Watson, an American Biologist.  Crick was much older, in his early 30s. Crick was now interested in molecular biology, and tissue culture, Watson in Biology and Xray crystallography, the latter subject being vital to the study of the structure of DNA. Watson and his father had been bird watchers interested in evolution but this did not give help in coming to grips with what a living human cell was.

In King’s College, London, Maurice Wilkins was working on the structure of DNA. He had made a wartime contribution to America’s nuclear project and was discouraged by the immense destruction it caused and now keen to work with living things and contribute to a biological field. His policy was to go on fiddling with a subject long after others had given up. Roslyn Franklin joined the department in 1950. She had expertise in X-ray crystallography.

Between Cambridge and London there was both a competitive race as well as friendly collaboration. Linus Pauling, later a Nobel prize winner, was also working on the same project in California Institute of Technology in America. There was no collaboration between him and the teams in England. At one moment a rumour that Pauling had worked out the matter and was about to publish, put the cat among the Cambridge ‘pigeons’ and but Cambridge was aware that Pauling was rather short on X-ray crystallography evidence. The Cambridge team too lacked this but their break came when Roslyn left the project at King’s to work on another subject. Crick visited King’s College and was shown the crystallography picture worked out by Roslyn. Later Crick admitted that it hit him like a bombshell, as he suddenly understood a crucial point. DNA molecule had a helical structure!

He later acknowledged Roslyn Franklin’s contribution to the unravelling of DNA structure.  Roslyn died of cancer five years after the discovery. But time has returned her to the rightful place in DNA history. Half a dozen books have been written about her and a University just outside Chicago renamed after her.
So all the research had come together. It went back to Mendel in the 19th century. He postulated that a particle was responsible for inherited characteristics. Other great scientists in the 20th Century like Frederick Griffiths and Owen Shargarth had noted the repetition of 4 bases in DNA i.e. Adenine, guanine, cytosine and thymine.  Watson and Crick had to work out how these bases fitted together.  They ‘moulded’ these bases to form the structure. The mood was ‘we can see the Port but we have not docked in the harbour yet’. A lot of hard work followed- continuous work for 4 days and suddenly the Eureka moment arrived! Everything fitted.  Suddenly the answer was there and it was beautiful. They were able to answer the problem of how genes replicate- very simple and you couldn’t miss it! The alternative team at Kings was satisfied that the model was right. When Maurice Wilkins of King’s entered the lab in Cambridge he saw a double helix model of DNA extending from the floor to ceiling. The news caused a hubbub in their favourite pub in Cambridge when they met their colleagues but when the article appeared in ‘Nature’ on the 15th April 1953 it didn’t cause a stir.

In 1962 Watson, Crick and Wilkins were awarded the Nobel Prize for the discovery of the molecular structure of the DNA molecule and its manner of transmitting information (Wilkins was the head of DNA project at King’s). A scientific revolution was set in motion. This was going to change radically the way we think about ourselves, was Crick’s surmise. There had been a revolution in physics since 1925 and now this was going to be a revolution in molecular biology.
In 1966 the genetic code of DNA was cracked. In 1972 the first recombinant DNA molecule was created. Suddenly there were ethical questions because of the possibilities this technology opened up. One could predict occurrence of diseases, and the big brother effect was obvious. BBC TV had a Panorama programme addressing all these issues. Do we have the right to choose the characters of unborn children? It was discussed that a body of responsible people should decide, analyse these questions and regulate application of knowledge. Should we close the Pandora’s box before things got out of hand?

But things didn’t go that bad. In 1990 the Human Genome Project was born. The task? To frequence the 3 billion bases in the human DNA molecule. This was a jigsaw puzzle of immense complexity. A working draft of the human genome was made in the year 2000. A parallel research was going on with DNA finger printing which brought its own eureka moment. This was down to Sri Alec Jeffries. This opened up the possibilities of pinning down the identity of people dead or alive. Mum, dad and child could be told apart and in the smudgy mess they identified the signs of tobacco, a mouse, a baboon and a Lima by accident.

Since 1987 DNA has been used in crime scene investigation, to convict criminals and save innocent victims. In one case a rapist was convicted because the victim left a lock of hair in the car and spat on the carpet. She had watched the popular CSI program on TV. DNA traces bones to it’s owner, a lady who claimed she was the escaped daughter of the Russian Czar was disproved by DNA, and the butcher of Auschwitz did indeed escape to USA and died there as his remains proved. DNA print has allowed scientists to travel back in time and find traces of people and animals in bones 1000s of years old. Tutan Karman’s early death was hastened by malaria. DNA helps in immigration cases and helps trace ancestry of persons. A well-known radio presenter always thought to be Scottish had a DNA check and was proved that he was Anglo Saxon with links to Denmark and King Macbeth and later was probably transported from Southern Scotland to Murray Firth!  Another was traced to have roots in the Middle East. It is known that the Jewish and Muslim share the same DNA and cannot be told apart but the person in question was thought to be Jewish as over 2000 years ago the Jewish emigration started with Diaspora widely spread over European countries.
The odds that a match is wrong are less than one in a billion!
A moral argument arises. Should the state hold on to a database of innocent people i.e. suspected of crime but cleared by DNA testing?
Should we all end up on it? It’s creepy and has gone too far. Higher percentage of black people’s DNA ending up on a database when it has no proportion to the population, is this discrimination? In England the National database has now been taken over by the Home Office. In the next 40 years many cancers will be prevented. Genetic research too depends on DNA database. Many are enthusiastic while some have concerns. Opportunity to opt out should be the way forward.

Copyright note:
The material above belongs to BBC radio 4.  Zita took the liberty to transcribe it.
Post script: Francis Crick died in San Diego California in 2004 aged 88. James Watson lives in Long Island now aged 85. He is reported as saying the following: I think people are born curious but they have it pounded out of them.


7 comments:

  1. Very interesting article Zita. Thanks very much and hope many find it useful as I did-
    -Speedy-

    ReplyDelete
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    Replies
    1. Dear Anonymous, you must follow James Watson's advice. We are born with initiative so don't let it be pounded out of you. I am not hot on technology. Please ask Mahendra's advice. And Lucky can tell you how to launch it. You've got to determine your readership and your contributors. And don't get discouraged if you don't get too much cooperation at first! Good Luck! Zia

      Delete