Raymond Gosling, Forgotten Hero of DNA

Raymond Gosling in later life (photograph by his wife)

Raymond Gosling (15 July 1926 – 18 May 2015) is the forgotten hero of DNA. As a lowly PhD student at King’s College, London, he took the famous “Photo 51” of DNA, but is not often given credit for doing so, perhaps because he was caught up in a story that was bigger than he was. A timeline helps elucidate the saga:

1949: Gosling joins King’s College as a PhD student under Maurice Wilkins.

1950: Gosling obtains the first clear X-ray image of DNA, using techniques developed with Wilkins. Wilkins presents this image at a conference in Naples in May, where it excites James Watson.

1951: Rosalind Franklin joins King’s College, taking over much of Wilkins’ work, which causes considerable friction. Gosling is told to transfer from supervision by Wilkins to supervision by Franklin.

November 1951: Franklin gives a talk suggesting that DNA is a helix (see her notes). Watson attends the talk, and later he and Francis Crick reveal a helical DNA model that turns out to be wrong.

May 1952: Gosling takes the famous “Photo 51” of DNA’s “B” form (below – and hear his account here), but Franklin requires him to work with her on the “A” form, which is much more difficult to analyse.

Raymond Gosling’s famous “Photo 51” of DNA’s “B” form, taken in May 1952

June 1952: Franklin begins making arrangements to leaves King’s College London for Birckbeck College.

July 1952: Based on the “A” form studies, Franklin decides that DNA is not a helix, and produces a mock death notice for the concept (below).

Rosalind Franklin’s mock obituary for the DNA helix idea, July 1952

January 1953: At Franklin’s suggestion, Gosling gives his “Photo 51” to Wilkins, who shows it to Watson a few days later. Watson immediately realises that it very clearly reveals a helix.

February 1953: Linus Pauling in the USA publishes a three-chain helical structure for DNA. This is a massive blunder – Pauling had forgotten that DNA is deoxyribonucleic acid – but it puts pressure on Watson and Crick to discover the DNA structure before Pauling fixes his mistake.

March 1953: Watson and Crick finish building their final DNA model, which integrates knowledge of the helix with their idea for AT and GC base pair bonding – and a great deal of effort in trying to make metal scale models of the molecules fit together in accordance with the laws of chemistry. That same month, Franklin leaves King’s College London, but continues to co-author papers with Gosling.

The structure of DNA

April 1953: Three DNA papers appear in Nature (without peer review!):

All three teams acknowledge each other – Watson and Crick acknowledge the unpublished work of the others; Wilkins and Stokes acknowledge discussions with the others; Franklin and Gosling acknowledge discussions with Wilkins, Stokes, and Crick.

1954: Gosling completes his thesis.

April 1958: Franklin dies of ovarian cancer. In the last years of her life, she, Watson, and Crick were close friends, and she recuperated from medical treatment at the home of Crick and his wife.

1962: Crick, Watson, and Wilkins share the Nobel Prize in Physiology or Medicine. Franklin is ineligible because Nobel Prizes cannot be posthumous, but Gosling gets nothing either. He is not the first PhD student to have their contribution go unrecognised. Or the last.

Science in stained glass

These four wonderful stained-glass windows at Gonville and Caius College, Cambridge commemorate Francis Crick (and the structure of DNA), neurophysiologist C.S. Sherrington (and a neuron), statistician Ronald Fisher (and a Latin square), and logician John Venn (and a Venn diagram). All photos are by Wikipedia user “Schutz.”

Pumpkin time!

It’s Halloween time, at least in the USA. There have been some interesting carved pumpkins around with scientific and mathematical themes, like Nathan Shields’ interpretation of “Pumpkin Pi” above. The legendary Will Gater also excelled himself last year, and Lenore Edman produced a great “DNA-o-lantern” a few years ago (photo below).

Greetings to everybody who celebrates the day!

The genetic code and its variations

The discovery of the structure of DNA by Watson and Crick in 1953, and the Crick, Brenner, Barnett, Watts-Tobin experiment of 1961 led to the elucidation of the genetic code, shown above. Triplets of the RNA letters “U,” “C,” “A,” and “G” (or the DNA letters “T,” “C,” “A,” and “G”) encode the amino acids Alanine (Ala/A), Arginine (Arg/R), Asparagine (Asn/N), Aspartic acid (Asp/D), Cysteine (Cys/C), Glutamine (Gln/Q), Glycine (Gly/G), Histidine (His/H), Isoleucine (Ile/I), Leucine (Leu/L), Lysine (Lys/K), Methionine (Met/M), Phenylalanine (Phe/F), Proline (Pro/P), Serine (Ser/S), Threonine (Thr/T), Tryptophan (Trp/W), Tyrosine (Tyr/Y), and Valine (Val/V). Consequently, long strings of DNA letters map to long strings of amino acids (that is, to proteins).

The genetic code is largely standard, but nevertheless comes in several variations, as shown above. For example, the “Stop” triplet UGA codes for Cysteine (Cys/C) in the nuclei of certain ciliate protozoa, and for Tryptophan (Trp/W) within most mitochondria (mitochondria not only have their own DNA, but they have their own genetic code for interpreting it). In the table above (click to zoom), colour indicates the number of different alternative meanings for each triplet, and “+” signs give a rough indication of how common an alternative is. The table shows several intriguing patterns.

The diagram below uses multi-dimensional scaling (with R) to visualise the differences between the various genetic codes, with the standard code in blue. The mitochondrial codes (yellow) have substantial variation, compared to nuclear codes (green). These variations in the mitochondrial codes are believed to be the result of random genetic drift.

The tree below (the result of neighbour-joining with R) offers a somewhat less informative view of the differences between the various genetic codes:

Powers of Ten: a short review of a short film

This short 1977 film by Charles and Ray Eames has become a classic, as has the 1957 Dutch book by Kees Boeke on which it was based. They have spawned numerous variations and adaptations, including a nice flip-book derived from the Eames film:

Short, sweet, and insightful, these little gems teach both important scientific facts and an appreciation of orders of magnitude.

* * * * *
Powers of Ten: 5 stars

The Cavendish

Photo: “RichTea”

The Cavendish Laboratory at Cambridge has had more than its fair share of major scientific discoveries. In this old building (which the Laboratory no longer occupies) worked James Clerk Maxwell, Lord Rayleigh, J. J. Thomson, Ernest Rutherford, Lawrence Bragg, James Watson, and Francis Crick, among others. Their discoveries included the electron, the neutron, and the structure of DNA. I’ve always wondered: did the genius ooze into the walls? Would I become a better scientist if I could sleep a night inside the old Cavendish building? Or would I see ghosts performing experiments?

The Cavendish opened on 16th June 1874, receiving a write-up in the (then new) journal Nature (10: 139–142, 25 June). A description by William Garnett is also available here. The inscription “Magna opera Domini exquisita in omnes voluntates ejus” was placed over the doors. This is taken from Psalm 110:2 in the Clementine Vulgate (Psalm 111:2 in Protestant Bibles). The English version, “The works of the Lord are great, sought out of all them that have pleasure therein,” was placed over the doors of the Laboratory’s new building.

In 1882 the Cavendish accepted women on equal terms with men, although the University itself did not award degrees to women until 1948. Eleanor Sidgwick was the first woman to work at the Cavendish (1880–1882). Elsa Neumann joined in 1899, and Katharine Burr Blodgett in 1924.

Photo: William M. Connolley

Phylogenetics and snails

A recent article in Wired highlights some interesting work by Leonidas Salichos and Antonis Rokas of Vanderbilt University, which they have recently published in Nature.

Salichos and Rokas point out the inconsistent phylogenetic trees produced by different DNA studies. There is disagreement, for example, on whether gastropods (left, below) are more closely related to bivalves (centre) or scaphopods (right).

Image on right by Hans Hillewaert, others public domain

Gastropods are grouped with scaphopods here, for example, but scaphopods with bivalves here.

While Salichos and Rokas give some answers, part of the problem, in my view, is the common tendency to use maximum-likelihood methods to produce a single phylogenetic tree. The standard algorithms will always produce such a tree of course, but it is important to give the equivalent of error bars, and indicate the range of possible trees supported by a given dataset. Phylogenetic networks, like the one below, are a way of doing this. Occasionally, the data forces us to say “we’re not quite sure” to some questions that have been asked.

Phylogenetic network by Katharina M. Jörger, Isabella Stöger, Yasunori Kano, Hiroshi Fukuda, Thomas Knebelsberger, and Michael Schrödl (see their paper)

The Double Helix, 60 years later

This photograph (by “Alkivar”) shows a reconstruction of the double helix model of DNA, constructed by James Watson and Francis Crick in 1953. The metal plates are molecular models of bases (some of these plates are original). The model is located in the Science Museum, London (see also their photograph).

This model not only led to one of the greatest-ever breakthroughs in biology (see the original 1953 paper, as PDF), but also demonstrated that “playing with models” was an effective way of doing chemistry. The discovery built on X-ray crystallography work by Maurice Wilkins, Rosalind Franklin, and Raymond Gosling (see their papers and the famous X-ray photograph produced by Gosling). Chemical investigations by Erwin Chargaff and others also produced essential information.

The breakthrough by Watson and Crick is commemorated by, among many other things, the Cambridge stained glass window shown below (located in the dining hall of Gonville and Caius College, photo by “Schutz”).