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From England:

From the Americas:

* if it proves difficult to form distinct layers of liquids, dissolve a little sugar in the curaçao.

Also required:

* adjust these volumes for smaller tubes.

Others have suggested (unpublished data) that thin helical twirls of lime peel may be used to decorate the rim of the tube. More enterprising drinkers have tried to recover the nucleic acid from the gin, using a swizzle stick. We are not aware of the details of the results of these investigations.

Most of the 'D.N.A.' in the gin is probably pectin, although the method described here is strikingly similar to the 'Marmur preparation' used by molecular biologists throughout the world to prepare D.N.A. [2].

It has not escaped our notice that this cocktail contains significant amounts of alcohol and should, therefore, be consumed only by adults and in moderation.

We are much indebted to Peter Finegold for suggesting that we create a cocktail to celebrate the anniversary.

D. R. MADDEN
J. W. SCHOLLAR

National Centre for Biotechnology Education
The University of Reading

This figure is purely diagrammatic. The D.N.A. precipitates in the gin.

CORRESPONDENCE RECEIVED

The following letter has been received:

Sirs

With regard to your DNA cocktail recipe.

Procedure
Strawberries and pineapple were purchased on the way home. Ice cold gin, lime juice and blue curaçao were available as standard reagents.

Results
There was no problem in replicating the separation of the gin and curaçao but the strawberry purée did not float in the way described in the original paper. The experiment was repeated with ice cold vodka but the same problem was encountered.

Discussion
It seemed likely at first that the protease digestion of the strawberries had not been successful. This could be facilitated by allowing longer time for digestion at a slightly elevated temperature. Suggestions that the strawberry preparation would benefit from further treatment, perhaps by filtration or centrifugation seem ill-founded as it is likely that cellulose debris lower the density of the preparation and that a filtrate or other concentrate would be even less buoyant.

Conclusion
We are forced to conclude that the results are irreproducible and that the authors should be asked to demonstrate their results to suitably qualified team of international experts, including the author of this critique.

Noel Jackson
Education Manager
Centre for Life, Newcastle-upon-Tyne

Authors' response
We suspect that Noel has used the fresh strawberries to which he is accustomed rather than frozen ones that were available to us in Reading. Others have reported that fresh strawberries are difficult to blend sufficiently. Fresh strawberries are something that we can only dream of down here.

DM, JS

MARTHA CHASE
It is with sadness that we note that Martha Chase died on 8th August, 2003 aged 75.

Chase conducted the now-famous 'Waring blender' experiment while still an undergraduate. Al Hershey wrote to Jim Watson about their as yet unpublished findings in April 1952, and Watson (who was by then working with Crick) reported them first to a meeting of the Society for General Microbiology in Oxford. Salvador Luria, another member of the phage group, was due to attend the meeting but like Linus Pauling had had his passport withdrawn by the US State Department during the McCarthy era, so it was left to Watson to bring the news.

Contemporary accounts suggest that the significance of the Hershey and Chase work was not appreciated by many present, although Watson was spurred on by the confirmation that DNA was the genetic material. Less than a year later he and Crick had the double helix.

An obituary of Martha Chase with more details and links to relevant Web sites may be found at:

http://www.biomedcentral.com/news/20030820/03

Copyright © National Centre for Biotechnology Education, 2006 | www.ncbe.reading.ac.uk