Who Invented The Punnett Square

Genetics. 2012 Sep; 192(ane): three–13.

Reginald Crundall Punnett: First Arthur Balfour Professor of Genetics, Cambridge, 1912

Abstract

R. C. Punnett, the codiscoverer of linkage with West. Bateson in 1904, had the good fortune to exist invited to exist the first Arthur Balfour Professor of Genetics at Cambridge University, United Kingdom, in 1912 when Bateson, for whom it had been intended, declined to leave his new appointment every bit commencement Director of the John Innes Horticultural Institute. Nosotros here celebrate the centenary of the kickoff professorship dedicated to genetics, outlining Punnett's career and his scientific contributions, with special reference to the discovery of "partial coupling" in the sweet pea (afterwards "linkage") and to the diagram known as Punnett's square. His seeming reluctance as coauthor with Bateson to promote the reduplication hypothesis to explain the statistical evidence for linkage is stressed, every bit is his relationship with his successor as Arthur Balfour Professor, R. A. Fisher. The groundwork to the establishment of the Professorship is also described.

THE centenary of the foundation of Cambridge University'due south Professorship of Genetics in 1912 provides a timely occasion to retrieve the contributions of its first holder, Reginald Crundall Punnett (1875–1967; Figure 1). Overshadowed by his senior colleague William Bateson (1861–1926), for whom the Professorship had been intended, and his successor R. A. Fisher (1890–1962), Punnett played an important role in the early on days of Mendelian genetics. He wrote the first genetics textbook Mendelism (Punnett 1905), collaborated in the discovery of partial coupling (linkage), asked G. H. Hardy the question that led to the formulation of what became known as Hardy–Weinberg equilibrium, published Mimicry in Collywobbles (Punnett 1915) and Heredity in Poultry (Punnett 1923a), and pioneered the use of sex-linked markers for sexing poultry chicks. He founded the Journal of Genetics with Bateson in 1911 and edited information technology alone after Bateson'southward death. He was the first Secretary and was later President of the Genetical Society of Groovy Britain. His name is immortalized in "Punnett'due south square" (Figure 2).

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R. C. Punnett. Courtesy of the Main and Fellows of Gonville and Caius College, Cambridge.

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Punnett'due south square, from the 2nd Edition of Mendelism (Punnett 1907).

F. A. E. Coiffure (Crew 1967) wrote Punnett'south biographical memoir for the Purple Society, to which Punnett was elected in 1912, and followed this with a shorter account for GENETICS (Crew 1968). In the opening paragraph of the latter he said that Punnett "had the adept fortune to be an active participant in the work that confirmed and extended the findings of Gregor Mendel when these were brought to lite in 1900. He lived, therefore, in a period that was filled with excitement and could rightly feel that he was involved in a cracking chance that would surely lead to a revolution in biological thought." Crew's memoirs should be consulted for details of Punnett'due south life; here I concentrate on his scientific contributions and give only a brief biographical summary.

Brief Biography

Punnett was built-in to George and Emily Punnett (née Crundall) at Tonbridge, Kent, on June 20, 1875. Both parents were of Kentish stock. He was educated at Clifton School, Bristol, and Gonville and Caius College, Cambridge, which he entered as a scholar in 1895. Originally registering as a medical educatee, he took the Natural Sciences Tripos, specializing in zoology in his third year and beingness placed in the kickoff grade in the Tripos in 1898. He spent the adjacent year at the Naples Zoological Station (Naples, Italy) and at Heidelberg University (Heidelberg, Frg) and in September 1899 accepted the post of Demonstrator in the Natural History Department of the University of St. Andrews (St. Andrews, Fife, Scotland). In October 1901 a Fellowship of Gonville and Caius College followed, capped by the Academy mail service of Demonstrator in Morphology, which he held until 1904, when he became Balfour Student in Zoology. This studentship, in memory of Francis Balfour, Professor of Animal Morphology, Arthur Balfour's brother, had been held by William Bateson from 1897 to 1900.

Then in 1908 Punnett started a rapid rise up the bookish ladder. However with his Caius Fellowship (which he was to retain until his death) he became Demonstrator in Animal Morphology in the Section of Zoology, Superintendent of the Museum of Zoology in 1909, and, when Bateson resigned his Professorship of Biological science in 1910 to take up the Directorship of the John Innes Institute, Punnett succeeded to information technology. In 1912 the Arthur Balfour Professorship of Genetics was founded and, following the failure of the University to attract Bateson back from his Directorship, Punnett was appointed. Nosotros consider the history of the Professorship in a later section.

At Naples in 1899 Punnett started to study the morphology of nemertine (or "Nemertean") marine worms, and these continued to be his main interest at St. Andrews and on his render to Cambridge. In 1903 he embarked on a statistical study "On nutrition and sexual activity-determination in man," using data for London from the 1901 Census, which revealed a modest facility in handling numbers (Punnett 1903). The human sex ratio was my own Ph.D. topic and in 1959 I must accept heard about his interest and sent him an offprint of 1 of my articles (Edwards 1958) for I still take his letter in reply.

Punnett's clan with Bateson started at the first of 1904. Some fourth dimension before, "Knowing that Bateson was carrying out Mendelian experiments at Merton House, Grantchester, [Punnett] wrote to him suggesting that perhaps his nutritional experiments might be and so designed that they would yield information apropos the inheritance of coat color [in the mouse]" (Coiffure 1967). When Bateson received an offer of financial support from his friend Mrs. Christiana Herringham in December 1903, he first thought of Leonard Doncaster equally an associate, merely Doncaster declined (Cock and Forsdyke 2008, p. 217) and and then he wrote to Punnett (on Christmas Day), inviting him to come "into partnership in my breeding experiments." "Mr. Punnett joined with enthusiasm, and very generously refused the ... salary" (Bateson 1928, p. 87), "... and so a partnership that was to last six years and that was to brand notable and enduring contributions to genetics came into being. The two men were very different temperamentally, Bateson was a forceful personality, antagonistic and stern; Punnett was retiring, tolerant and friendly; it was a happy and harmonious partnership" (Crew 1967).

In 1913 Punnett married Eveline Maude Froude, widow of Sidney Nutcombe-Quicke. They lived in Whittingehame Gild, Storey's Way, Cambridge, in the house provided for the Arthur Balfour Professor, until Punnett retired in 1940 at the age of 65. He and his wife so moved to Bilbrook, near Minehead, Somerset, where he died on January 3, 1967. There were no children.

Crew's (1967) biographical memoir contains a list of Punnett's publications and summaries of his work beyond the topics I hash out in detail here. In the summer of 1909 Punnett had visited Ceylon to study mimetic collywobbles, where he met his Caius colleague R. H. Lock, then Assistant Manager of the Royal Botanical Gardens at Peradeniya (Sri Lanka). The visit led to a handsomely illustrated book Mimicry in Butterflies (Punnett 1915). "... it included a mutationist's explanation for the development of complex mimetic resemblances between members of unrelated species" (Bennett 1983, p. eight). R. A. Fisher's view of their development was completely different. He set it out in Fisher (1927) and in Affiliate Eight, "Mimicry," of The Genetical Theory of Natural Selection (Fisher 1930a) with special reference to Punnett's view in the section "The theory of saltations." Provine (1971, p. 150) gives an account. On evolution Fisher and Punnett were to cross swords again when Punnett reviewed The Genetical Theory, which we refer to below under Population Genetics.

Punnett'due south experience with studying Mendelian characters in poultry led him to invent the method of using sex-linked plumage color factors to sexual practice twenty-four hours-erstwhile chicks, thus enabling the unwanted majority of cockerels to be disposed of immediately. By 1940 he had published, alone or jointly, 11 "Genetic studies in poultry," with another two to come in retirement in 1948 and 1957. Crew (1968) may exist referred to for further details, for unlike the biographical memoir for the Regal Order his memoir in GENETICS contains a substantial excerpt by Professor F. B. Hutt "whose Genetics of the Fowl is in the directly line of Punnett's Heredity in Poultry, 1923a" (Crew 1968).

Punnett (1928) edited Bateson's scientific articles for Cambridge Academy Press. T. H. Morgan (1929) reviewed the two volumes in Nature, regretting the omission of the Reports to the Development Committee (see below), which were represented only by summaries. After Bateson's death in 1926, Punnett (1926) wrote a memoir of him in the Edinburgh Review, function of which was reprinted in Notes and Records of the Royal Society in 1952 (Punnett 1952).

Punnett's Square

he work for which Punnett is all-time remembered, the discovery of linkage jointly with William Bateson, arose out of their studies of Mendelian ratios in the sweet pea Lathyrus odoratus. The discovery is more than properly referred to as "partial coupling" because the word "linkage" had not yet been coined in this connectedness, nor had its chromosomal basis been postulated. The assay of the diverse ratios that characterized Mendelian inheritance was much facilitated by Punnett's simple square diagram showing how gametes combine to make zygotes or sometimes how genotypes at two loci combine to make zygotes. Punnett'southward square seems to have been a development of 1905, as well belatedly for the kickoff edition of his Mendelism (May 1905) simply much in evidence in Report 3 to the Evolution Commission of the Royal Guild [(Bateson et al. 1906b) "received March 16, 1906"]. The primeval mention is contained in a letter of the alphabet to Bateson from Francis Galton dated October 1, 1905 (Edwards 2012). Nosotros have the testimony of Bateson (1909, p. 57) that "For the introduction of this system [the 'graphic method'], which greatly simplifies hard cases, I am indebted to Mr. Punnett." As we shall see, 1905 was likewise an of import year in the discovery of fractional coupling, so the two developments went hand in manus. Here we give the salient features of Punnett's foursquare, relying on the extended account by Edwards (2012), which is fully illustrated.

The first published diagrams appeared in 1906. On February 1 Bateson, in an address to the Neurological Gild (Bateson 1906), displayed the ix:3:3:ane Mendelian ratio among the F_two for two loci when dominance is complete at both. Then Report III contained several, notably the ones on p. 3 (our Figure 3) and p. ten. Figure three displays the 9:7 ratio obtained when, to quote the figure legend, "The grapheme, colour for example, appears simply when C and R meet." We consider the more circuitous figure on p. 10 in a moment. Figure 3 was repeated by Lock (1906, p. 199) in his book Contempo Progress in the Study of Variation, Heredity, and Evolution, the Preface beingness dated Oct 23. It will exist noted that these squares are formed by the simple process of laying out the four gametotypes CR, cR, Cr, cr as headings for both rows (paternal gametes, say) and columns (maternal gametes) and "adding" them to create the entries in the squares corresponding to the zygotes formed by their unions.

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Punnett's square, from Report Three (Bateson et al. 1906b).

Yet, when Punnett published the second edition of his Mendelism, he used a slightly different format (our Figure two; Punnett 1907, p. 45) also displaying 9:3:3:1. It is divided into four large squares each of which contains iv small squares. Each large square is identical in respect to the second locus, B,b, and shows the two types of gamete uniting to grade zygotes, two of which, Bb and bB, are identical if gametic origin is ignored. The four large squares practise the same for the offset locus A,a, and and so the iv small-scale squares for B,b are added to each of the large squares for A,a. Of form information technology comes to the same thing equally Figure iii, the difference being just a matter of the labeling. In the 3rd edition (Punnett 1911, p. 34) he reverted to the arrangement of Effigy 3 complete with a clarification of the structure of what he called the "chessboard" method (although in truth it is more than like a multiplication table).

When 3 loci are involved, an 8 × 8 square results, as given in Report Iii on p. ten (Figure four). This is an extremely interesting construction. Thinking of it equally 4 large squares, we run into that in respect to B,b and R,r, each of these squares is the aforementioned, simply different from either of the methods of constructing a two-locus table so far described (in fact there is an mistake in columns 7 and eight, where the lower entries in row 5 take been interchanged). Instead of the marriage of gametes we have the spousal relationship of loci, the rows for R,r, and the columns for B,b. And so each of these squares has been dropped into a square for C,c as in Punnett'southward (1907) construction (Figure 2). This hybrid format was suggested by Sir Francis Galton in a letter to Bateson dated October ane, 1905 containing the original of Figure four (reproduced in Edwards 2012). It is odd that when information technology was published, in Study 3 and later, Galton'southward help was not acknowledged.

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Galton'south iii-locus square from Report III (Bateson et al. 1906b).

To appreciate the significance of Galton's arrangement information technology is necessary to describe the situation that confronted Bateson and Punnett, and since the experiments involved are the very ones that led to the discovery of fractional coupling, this serves as an introduction to the next section. "The work was begun," wrote Bateson in his book Mendel'due south Principles of Heredity (Bateson 1909, p. 89), "by crossing two white sweet peas belonging to the diversity Emily Henderson. These plants were alike in every respect so far as could be perceived, excepting that the shapes of the pollen grains differed, the one having the normal long pollen grains of the species, while the other had roundish grains. The object of the experiment was to trace the descent of the pollen-graphic symbol and at the beginning no question of colour was entertained. When F_i was grown however it was clear that hither was a remarkable opportunity of studying a reversion in color due to crossing, for these plants instead of being white were purple like the wild Sicilian plant from which our cultivated sweet peas are descended."

Proceeding to the F_two, Bateson and Punnett found "phenomena [which] … presented superficially an appearance of nifty complexity. … It is unnecessary to get through the long series of steps by which the analysis of the phenomena was carried out. The meaning of the facts is at present perfectly clear and they tin all be arranged in 1 consequent scheme" (Bateson 1909, p. 90). They worked out that three loci would do. The ii original whites were CCrrBB and ccRRbb, leading to F_ane all CcRrBb. On selfing, these would lead to the 64 combinations shown in Figure 4. In the presence of C (for color?) the state of affairs is ever that R (red) ascendant to r gives a cerise blossom to which B (blue) dominant to b adds blueish to make a purple bloom, although in the absence of R there is no bluish lonely. This is so the blueprint in the three large squares corresponding to CC, Cc, and cC. In the 4th, cc, no colors of whatsoever kind appear. We end upwardly with 3 × 9 = 27 purples, three × 3 = 9 reds, and iii × 4 + 16 = 28 whites. The numbers given in Report III are 1634, 498, and 1593, respectively, 3725 in all, confronting expectations of 1571, 524, and 1630 (χ ² on two d.f. = 4.59, P = 0.10; all values of χ ² quoted hither are newly calculated).

Partial Coupling (Linkage)

It is frequently said that linkage was discovered by Bateson and Punnett in 1905. Thus A. H. Sturtevant himself, writing A History of Genetics in retirement (Sturtevant 1965), records (p. 40) that "Incomplete linkage was first reported in the sweet pea by Bateson and Punnett (1905)," but already some qualifications are needed. Offset, "in the sugariness pea" needs to be in parentheses, or at to the lowest degree between commas, because this was the start report of fractional linkage in any organism. Second, the reference is actually to Bateson et al. (1905), as given by Sturtevant in his bibliography, which raises the question of the contribution of Saunders. (Morgan 1928, in The Theory of the Factor, p. 323, went further and omitted Saunders from the reference too.) Third, the word linkage in its genetical context had not, in 1905, been coined and is associated with the chromosomal theory advanced by Morgan (1911), who even then nevertheless used the term "coupling." The start use of linkage in this connection is in 1912 (Morgan and Lynch 1912), but nosotros should notation that Bateson (1906) had written "We accept proof that in sure cases a character, say of shape, may be so linked or coupled with another graphic symbol, say of colour, that all or a majority of the germs [gametes] which carry the one carry the other likewise." Punnett (1911, p. 87), in the third edition of his Mendelism, wrote "In some way or other the factors for blueish and for long pollen become linked together in the cell divisions that give rise to the gametes, but the linking is non complete."

In the present business relationship I use coupling for the statistical bear witness as opposed to its chromosomal explanation, and, similar Bateson and Punnett, I distinguish between complete coupling and fractional coupling. This distinction is of import, because complete coupling had already been found by Correns (1900) in stocks (Matthiola) as noted by Bateson and Saunders (1902), who reported like "correlation" in their own experiments with stocks. Correns had used the give-and-take "gekoppelte." Although this 1902 Report to the Evolution Committee of the Imperial Social club (Bateson and Saunders 1902) was the joint work of Bateson and E. Rebecca Saunders ("Becky"), Part I, in which the correlation was noted, is headed "Experiments with Plants, carried out past E. R. Saunders," to whom therefore we may attribute the observation.

Partial coupling appears for the first time in Report Ii to the Evolution Commission (Bateson et al. 1905; received May 18, 1904), the one to which Sturtevant referred. It contains no further reference to correlation in its Matthiola section, but in the department on sweet peas we read "There is, therefore, some coupling of pollen-shape and colors" (italics original) (Bateson et al. 1905, p. 89). This department is headed "Experiments carried out by Westward. Bateson, E. R. Saunders, and R. C. Punnett (in 1904)." It is evident that many additions to Report II were made afterward May 1904, including a "Note added Dec 1904" at the finish. The earliest mention of disturbed segregations corresponding to this coupling is in Bateson'due south Written report to the Committee on Experimental Studies in the Physiology of Heredity at the British Association meeting in Cambridge in Baronial 1904 (Bateson 1905) and his Presidential Address to the Zoological Section at the coming together (also reproduced in Bateson 1928; the mention is on p. 255).

Then in Written report Iii (Bateson et al. 1906b; received March xvi, 1906) there is a full department on "Gametic Coupling," which starts "Early in the revival of convenance experiments, attention was called, specially by Correns, to the miracle of coupling betwixt characters. .... Examples of partial coupling accept not hitherto been adequately studied. A remarkable example occurs in regard to the distribution of the pollen-characters in F₂ from the white long 10 white circular Sweet Pea" (Bateson et al. 1906b, p. 9), and the results are printed. More information is given in the later department of Study Iii devoted to the sweetness pea itself ("Experiments by Due west. Bateson, E. R. Saunders and R. C. Punnett"). The crucial results had in fact appeared before in a brief note in Proceedings of the Royal Society, Series B (Bateson et al. 1906a; received December 1 and read December 7, 1905).

Finally, Written report IV (Bateson et al. 1908) contains, in its introduction, a cursory review of work on fractional coupling, which starts "The majority of our Sweet Pea work of the past two seasons was undertaken with a view to farther elucidating the phenomenon we have termed gametic coupling" (Bateson et al. 1908, p. ii). The section on sweet peas is headed "Experiments past W. Bateson and R. C. Punnett" and contains a subsection "Partial Gametic Coupling."

There is some slight evidence that Sturtevant, in his History, might knowingly have credited this discovery of partial coupling to Bateson and Punnett, omitting Saunders. Although Saunders was the undoubted Queen of Matthiola, Punnett does seem to accept been Rex of Fifty. odoratus. Sturtevant (1965, Author's Preface, p. eleven) had "some direct personal contact" with Bateson and Punnett and had met Saunders, although she counted among those he "never really knew." Bateson (1906), when discussing color in the sweet pea, refers to "an elaborate series of experiments made by Miss Saunders, Mr. Punnett, and myself," but in the corresponding part of his book Mendel'south Principles of Heredity (Bateson 1909, p. 89) he refers to experiments every bit having been "carried on jointly past Mr. Punnett and myself for some years." Nor is in that location any sense that he is inclined to neglect Saunders' work, for the next department (Bateson 1909, p. 95) on "Colors of Stocks" (Matthiola) starts "The experiments of Miss E. R. Saunders take revealed ... ." For farther information about Saunders see Richmond (2001, 2006) and references therein. Lock (1906, p. 200), a member of Bateson'southward group at the fourth dimension, says firmly "This phenomenon of partial gametic coupling was discovered by Bateson and Punnett in the Sweet Pea." Punnett (1914) himself was characteristically self-effacing: "Bateson in 1905 was the kickoff to describe in sweetness-peas a remarkable case in which 2 characters each exhibiting ordinary Mendelian segregation yet showed a peculiar distribution with regard to one another." Report 2 refers to "the original crosses of 1901." Punnett joined the sweet-pea piece of work in 1904, growing the F₂ in which he and Bateson noted the disturbed segregations, so the F₁ must have been 1903, which would make the original cross 1902. Perhaps there were some in both 1901 and 1902.

In his reminiscences "Early on days of genetics" given at the hundredth meeting of the Genetical Society at Cambridge in 1949, Punnett (1950) said "Sweet peas were the other main line of inquiry. We grew some thousands each year and of grade the garden at Merton House [the Bateson home in Grantchester] could non nearly accommodate such numbers." He goes on to draw the additional plots on the Academy Farm at Impington, four miles away, and the ride there "for a long afternoon, Bateson with his wife in the trailer conveying the 'Subcontract Book' and a microscope." "Ane of us pulled the constitute and sung out its characters and handed the plant to the other, who, with the microscope perched on some odd box picked up at the farm, determined the shape of the pollen. All duly logged past Mrs. Bateson" (Punnett 1950).

The "Subcontract Books" and allied notebooks recording experimental data are preserved in Cambridge University Library and might provide further information nearly the participants, if only past the handwriting. But no doubt they all helped each other, and information technology looks as though Mrs. Bateson deserved a formal mention as well.

Bateson and Punnett establish an F₂ segregation 2844 long pollen and 881 round, against three:1 expectations of 2794 and 931, respectively (χ ² on 1 d.f. = 3.62, P = 0.057). As we take seen, in the field they scored the color before the pollen type so it would be natural to take iii columns for the colors, each divided into 2 for the pollen blazon, and this is how the data were presented in Report Three (Table i). They noted that the three:1 ratio did non hold for the three color types individually. There seemed to be some kind of coupling of round with red and long with purple that was disturbing the Mendelian segregations; white seemed to be unaffected. Bateson and Punnett's explanation was that B (blue) and L (for long) tended to acquaintance in the gametes, equally did their recessive counterparts b and l (round). The converse to this coupling was the "repulsion" of B and l, b and Fifty.

Tabular array 1

F₂ segregation in the sugariness pea for blossom colour and pollen blazon

Purple		Red		White
Long	Circular	Long	Round	Long	ound
1528	106	117	381	1199	394

They were familiar with Mendel's law of independent segregation and with the complete coupling reported by Correns and past Saunders, but here was something in between, fractional coupling. "The significance of such partial coupling is obscure, and it may result from several processes, between which no discrimination can however be made" (Bateson et al. 1906b, p. nine) (Written report Iii). But it could be measured, and Bateson and Punnett institute that if gametes were produced in the ratio 7BL:1Bl:1bL:7bl, the resulting phenotypic ratio 177BL:15Bl:fifteenbL:49bl fitted the observed numbers (Table 1) quite nicely. The adding of the phenotypic ratio from the gametic for an F₂ segregation is now an elementary student exercise, but Report Three did non explain it, and neither did Bateson (1909) in his book. The general result for the gametic ratio

was given in Report Iv (Bateson et al. 1908) and past Punnett in the third edition of Mendelism, with a full explanation for the above case (Punnett 1911, Appendix to Chap. IX, p. 88):

threen ²−(2n−1)B L:(2n−1)B 50:(2n−1)b Fifty:iiin ⁱⁱ−(twon−ane)b 50.

(In fact, Punnett has a sign wrong in the gametic ratio.) Following Bridges (1914), nowadays we would use the recombination fraction θ = 1/northward with the gametic ratio

to give the familiar

$\frac{1}{2} + \frac{1}{4} {(1 - θ)}^{ii} : \frac{1}{2} θ - \frac{1}{4} θ^{2} : \frac{1}{2} θ - \frac{one}{four} θ^{two} : \frac{1}{4} {(1 - θ)}^{2} .$

Alas, it did not occur to Bateson and Punnett that the "several processes" they could contemplate for the explanation of partial coupling need non exist express to integral values of due north, and they became fixated on the further idea that north had to be a ability of two ["pure numerology brought almost by a fixation on Mendelian ratios" (Edwards 1996)], for they began to visualize processes of gametogenesis that required this every bit an caption, their and so-called "reduplication" hypothesis (Bateson and Punnett 1911; meet below). If they had kept an open mind and allowed any value of n, or improve still worked with the simpler θ, they would accept been complimentary to choose the best value without restriction. As late as March 1911, the engagement of the Preface to his 3rd edition of Mendelism, Punnett writes (Punnett 1911, p. 87) "Nor for the present can we suggest why certain factors should be linked together in the peculiar way that we accept reason to suppose that they are during the process of the formation of the gametes."

Weldon (1902) had already applied Karl Pearson's goodness-of-fit exam to Mendel's data, so that Bateson and Punnett could have called the value that gave the best fit by the criterion of χ ⁱⁱ, thereby inventing the method of minimum χ ^two almost a decade before Engledow and Yule (1914) did so (reprinted with a commentary by Edwards 1997). But that would have been stealing the biometricians' clothes.

We conclude by noting that Punnett made a very prescient remark well-nigh partial coupling when addressing the Epidemiological Section of the Royal Order of Medicine on February 28, 1908, three years before Morgan's chromosomal linkage theory. "Plenty, however, is known to make it certain that it [fractional coupling] oftentimes plays an important office in heredity, and I have laid some stress upon it because it may eventually be found to throw lite upon the declared association of sure physical peculiarities in man with particular forms of disease" (Punnett 1908). The comment foreshadows the suggestion by Fisher (1935) in "Linkage studies and the prognosis of hereditary ailments" read to the International Congress on Life Assurance Medicine (see Edwards 2004, for Haldane'southward possible contribution), which in plow foreshadowed the similar suggestion by J. H. Edwards (Edwards 1956) in connectedness with detecting marker loci in amniotic cells. For if a affliction cistron is linked closely plenty to a marker locus, knowledge of the mark genotype may aid in the prognosis of a disease not yet manifest. Punnett also remarked, in 1907 (Mendelism; Punnett 1907, p. 64), that "in that location is every probability that, equally it [partial coupling] becomes better known, it volition be constitute of peculiar importance in the elucidation of the architecture of the gamete." In his last edition (Punnett 1927, p. 135) he reminded us of this by quoting it, calculation "How brilliantly this prediction has been fulfilled by Professor Morgan and his colleagues will appear in the post-obit chapter [the chromosome theory]."

The Reduplication Hypothesis

For many years neither Bateson nor Punnett accepted the chromosomal caption of linkage, and by "coupling" and "repulsion" they meant statistical associations equally observed in the sweet pea. In a talk in 1959 Punnett said "I have sometimes been asked how it was that having got then far we managed to miss the necktie-up of linkage phenomena with the chromosomes. The answer is Boveri. Nosotros were deeply impressed by his paper 'On the Individuality of the Chromosomes' and felt that whatever tampering with them by way of breakage and recombination was forbidden" (Punnett 1950). In 1911 they advanced their "reduplication" hypothesis to explain coupling and its mirror phenomenon, repulsion. Its origin can be seen in some comments by Bateson in Mendel's Principles of Heredity (1909, pp.157–161), just the definitive account is in Bateson and Punnett (1911). By the time Whitehouse (1965) wrote his magisterial Toward an Understanding of the Mechanism of Heredity it had been forgotten. We use Sturtevant's (1965) historical business relationship:

According to the reduplication hypothesis, segregation does non occur at the time of meiosis just somewhat earlier, and not necessarily at the same time for each pair of genes. The cells that are finally produced, each with a unmarried set of genes, then multiply at different rates to requite the observed ratios. It is not easy to see why this scheme was adult, since there is null in it that seems related to the (2ⁿ–1):1 series, nor is in that location any independent evidence for the complex and symmetrical pattern of divisions that information technology requires. The hypothesis is related to Bateson'due south reluctance to believe that segregation occurs at the meiotic divisions (Sturtevant 1965, p. 40).

Sturtevant continues with further comments on Bateson's thinking. For more data about the hypothesis and Bateson'south reluctance to accept the chromosome theory see Erect (1983), who, interestingly, headed his section on information technology "Bateson'south ain rival theory," and Cock and Forsdyke (2008). The best that tin can exist said for the theory is that it seems to have spurred Morgan on to have his eureka moment in 1911 with the chromosomal explanation of linkage.

Punnett himself never incorporated reduplication into the later on editions of his Mendelism, limiting his discussion to observations on the numerical ratios idea to be occurring. He pursued the question with further experiments in sweetness peas (Punnett 1913, 1917a), merely by the second of these articles he was already considering Morgan'southward explanation of linkage, and in the 5th edition of Mendelism (Punnett 1919, p. 133) he introduced a new chapter, "The Chromosome Theory" "to present the position of the supporters of the chromosome theory ... [which] is, at the present moment, the most keenly discussed question in heredity." But the controversy was not really beingness discussed any more, and one senses that his heart was not in reduplication and he but did not want to upset Bateson.

Bateson (1922) famously abandoned his doubts "later on a week in close communion with the wonders of Columbia University" visiting Morgan'due south laboratory. The observations of the Belgian cytologist F. A. Janssens published in 1909 had persuaded Morgan and most other people of the beingness of crossing-over sufficient to account for the observed linkage phenomena, even though doubtfulness remained about Janssens' precise model (encounter the Perspectives by Koszul et al., 2012, in GENETICS, Vol. 191, Num. 2). Morgan was to write, in The Theory of the Gene (Morgan 1928, p. 41) "From the nature of the example it is practically impossible to demonstrate, even when twisting of the chromosomes is admitted, that it actually leads to an interchange of the kind demanded by the genetic evidence."

What did Punnett really think? According to Cock (1983) "At no fourth dimension did Punnett show whatever great interest in chromosomes," and I suspect that Punnett, who possessed "a blithe, kindly, open-air personality" (Needham 1967) quite unlike the combative Bateson, might simply have opted for a quiet life. Cock (1983) continued "He is unlikely, therefore, to have given Bateson any stimulus toward a more favorable view of chromosome theory." There is as well the possibility that he was sensitive to the view of his friend Lock, who had suggested equally early equally 1906 (Lock 1906, p. 252) that coupling might exist due to "some mechanism which causes the representative particles of the corresponding characters concerned to remain in company during the process by which the other allelomorphs are being reassorted between the chromosomes," as had been noted by Morgan and his colleagues (Sturtevant 1965). Even when describing the zygotic ratios arising from gametic coupling in his 1919 edition of Mendelism, Punnett (1919, p. 124) does not describe the reduplication hypothesis, merely maxim "More recently the term 'reduplication' has been brought into utilise. …. The term is non altogether satisfactory, for biologists are non at present in agreement as to the manner in which these gametic series come to exist formed." Torn between Bateson and Lock, it would accept been charactistic of Punnett to have kept his head downward, and in any case from 1911 Bateson was at the John Innes Institute and not in Cambridge.

The Arthur Balfour Professorship of Genetics

The prehistory of the Arthur Balfour Professorship starts non with Punnett, but with Bateson, whom the University fabricated a Reader in 1908. In their Report the recommending body, the General Lath, had said that "they regret that in view of the country of University finances they cannot propose at the present fourth dimension to establish a Professorship in Heredity and Variation" (Cambridge Academy Reporter 1907–1908, p. 213). The academic and political background to this engagement is fully described by Cock and Forsdyke (2008, p. 303). Evidently wheels were turning behind the scenes, for on February 24, 1908 the University'due south Council was able to publish a report "on a proposed Professorship of Biology" (Cambridge Academy Reporter 1907–1908, p. 632; reprinted in part in Cock and Forsdyke, p. 306). An anonymous benefactor, likely to have been Arthur Balfour, had offered to support in function a Professorship to be devoted to "that co-operative of Biology at present entitled Genetics (Heredity and Variation)" for 5 years in connection with the celebration of the Darwin centenary in 1909. Indeed, he wanted information technology to be the "Darwin Professorship," but the Quango thought a title should wait until "the professorship can … exist placed on a permanent footing." The duty of the Professor was quite specific: "to promote past teaching and research the knowledge of Genetics." Information technology was less than three years since Bateson had coined the word. The Professorship was clearly intended for him, and his election was announced on June 8. He gave his Countdown Lecture "The Methods and Scope of Genetics" on October 23 (Bateson 1908) and it is from 1908 that Cambridge's Professorship of Genetics actually dates. For Punnett the "musical chairs" of posts led to the changes already mentioned in the biographical section to a higher place, culminating in his election to this Professorship of Biology when Bateson resigned information technology to take up the Directorship of the new John Innes Horticultural Establish in 1910.

Arthur James Balfour (1848–1930) was Prime Minister from 1902 to 1905, a brilliant aristocratic intellectual who held a central position in the Conservative party for nearly l years. He was the elderberry brother of Francis Balfour, who had lost his life in a climbing accident in 1882 soon after becoming Cambridge's Professor of Animal Morphology. He had taught the undergraduate Bateson. Arthur Balfour's many connections included his brother-in-law Lord Rayleigh, Chancellor of the Academy at the time of the Darwin Centenary, an office to which he himself succeeded in 1919. He was President of the British Association at the time of the 1904 Cambridge coming together and the foundation President of the Genetical Society in 1919, being succeeded on his death by Punnett. Among his undergraduate friends he counted George Darwin, with whom he played existent ("court") lawn tennis, and George had taken him to visit his father Charles Darwin at his house in Downe, Kent. "The kindness of the bang-up man, his sympathy and charm, exceeded all that could exist demanded by the most self-centered invitee, and left a deep impression on my youthful mind" (Balfour 1930, p. 38). Bateson could non have had a more than powerful friend at court than Arthur Balfour.

During the 1909 Cambridge Darwin celebrations Balfour was chosen to propose Darwin's "immortal retention" at the banquet on June 23. That morning time the Chancellor, Lord Rayleigh, had ended his address of welcome to the delegates past maxim

During the last generation, Cambridge, especially since the time of Michael Foster, has been active in biological work. We have the men and the ideas, but the difficulty has always been lack of funds. At the present time it is desired, among other things, to found a Chair of Genetics – a subject closely associated with the proper name of Darwin and of his relative Francis Galton, and of the greatest possible importance, whether it be regarded from the purely scientific or from the practical side. I should like to recollect that the involvement aroused by this Celebration would have a applied outcome in better provision for the hereafter cultivation, in his own Academy and that of his sons of the field wherein Darwin labored (Cambridge University Reporter 1908–1909, p. 1372).

The plea did non autumn on deaf ears. In July 1910 Balfour wrote a short article dealing with the endowment of the report of Genetics in the University. Late in 1911 a meeting was held at Balfour's house in London, equally a outcome of which an anonymous benefactor placed in the hands of Balfour'south friend Viscount Esher the sum of £twenty,000 to endow a Professorship to be called the Balfour Professorship of Genetics (Cambridge University Reporter 1911–1912, p. 694). Regulations were drawn upward, which stipulated that the initial appointment should be fabricated by Balfour and the Prime number Minister jointly. It was also decided that the title should be the Arthur Balfour Professorship to avoid confusion with Francis Balfour.

Balfour wrote to Bateson, inviting him to accept the Professorship, but Bateson, unwilling to render from his Directorship of the John Innes Institute, declined and suggested that Punnett "is in every manner worthy to be appointed" (Erect and Forsdyke 2008, p.386). And and then he was, on November eleven, 1912, being formally admitted at the Congregation on November 22. Whittingehame Lodge, the Professor's house, was presented to the University in 1914 past Viscount Esher and Arthur Balfour, past and so an Earl.

Punnett's legacy to Cambridge Academy as Professor was modest. When his successor R. A. Fisher was elected in 1943, he institute no staff and no students, but the large firm, Whittingehame Society, intended for his occupation. "With the coming of state of war, the business firm was let to tenants and the land plowed up by the War Agronomical Committee. The department ceased to exist" (Box 1978, p. 398). Fisher was able to live in Caius College, since his Fellowship had been renewed on his return to Cambridge. Between 1943 and his retirement in 1957 he used the house and garden to develop a small-scale Department and start a 3rd-year Natural Sciences Tripos subject, "Genetics." Nowadays the Section thrives, and one valuable direct legacy of Punnett's remains to this twenty-four hour period: his collection of offprints and many of his books.

However, Punnett influenced the young Fisher, who was a student in Caius College in 1909–1913 during which time he helped to found the Cambridge University Eugenics Society, approaching Punnett, one of the dons who was a member of the national Society, to serve on its Quango. Punnett gave a lecture at the second public meeting of the University Society on December five, 1911. "The undergraduate committee of the Society institute Punnett'south exposition of Mendelism so important that, at a coming together in Fisher's rooms [in Caius] the following term, Fisher every bit chairman proposed that they should make it a dominion that each bookish year one paper be devoted to an elementary exposition of the principles of heredity, meaning, of class, Mendelism" (Mazumdar 1992, p. 99).

From 1920 to 1926 Fisher was a Fellow of Caius at the same time as Punnett and though non resident he would have met him frequently. It was Punnett who, with Karl Pearson, reported unfavorably for the Royal Club on Fisher's (1918) famous commodity "The correlation between relatives on the supposition of Mendelian inheritance," prompting Fisher to remark to Westward. F. Bodmer in 1956 "My 1918 newspaper was refereed by Pearson and Punnett, both of whom I later succeeded" [personal communication; encounter also Fisher's letter to C. S. Stock, November 18, 1943, replying to Stock'south letter congratulating him on election to the Arthur Balfour Professorship (Bennett 1983, p. 264)]. All things considered, Fisher did not accept a high academic stance of his predecessor. I requite some of the reasons for this below. Punnett had gone to his Somerset retirement before Fisher returned to Caius, and although they overlapped as Fellows until Fisher died in 1962, Punnett did non return often and in that location is no corporate memory of their interaction when he did.

Population Genetics

The story of Punnett'south friendship with the mathematician G. H. Hardy and how information technology led to Hardy'due south 1908 discovery of "Hardy–Weinberg equilibrium" at the aforementioned fourth dimension as West. Weinberg'southward has often been told, not always correctly. In itself it reveals little of Punnett except that he was puzzled by something that actually is extremely simple, and he had to get Hardy to set him straight. The fullest and, I hope, about accurate, account is to be found in a recent Perspectives (Edwards 2008).

Later on, when writing his volume Mimicry in Butterflies, Punnett (1915) appealed to Hardy for some more than mathematical help. He wanted to know the effects of pick at a single Mendelian diallelic locus under random mating, and Hardy, perhaps aware of the corporeality of computation involved, passed the problem on to his Trinity pupil H. T. J. Norton. The results were published in tabular form in Appendix I of Punnett'southward (1915) book (and reprinted in Provine 1971). They were very influential, among other things inspiring J. B. South. Haldane to initiate his long series of articles on option. Haldane was appointed Reader in Biochemistry at Cambridge in 1923, with a Fellowship of Trinity, and wrote that in 1922 Norton had shown him some calculations that were eventually published in 1928 (Haldane 1927; Norton 1928). Provine (1971) may be consulted for further details and Charlesworth (1980) for details of "Norton'southward theorem."

In 1917 Punnett once again sought Hardy's help over a similar problem, and this fourth dimension Hardy himself calculated how slowly a recessive lethal is eliminated from a population, thus apparently discrediting the eugenicists' claim that deleterious recessives could exist eliminated in a few generations (Punnett 1917b). However, Fisher (1924) countered that these calculations "have led to a widespread misapprehension of the effectiveness of choice."

Punnett (1930a) reviewed The Genetical Theory of Natural Choice (Fisher 1930a) for Nature. It was not friendly. Fisher (1930b) replied in a alphabetic character to Nature, to which the editor allowed Punnett (1930b) an immediate rejoinder. We now know, what Fisher could not accept known at the time, exactly what Punnett reported to the Purple Society about Fisher's "1918" article (Norton and Pearson 1976): "I have had another go at this paper only frankly I do non follow it owing to my ignorance of mathematics." He concluded "I do not feel that this kind of piece of work affects us biologists much at present. It is besides much of the lodge of trouble that deals with weightless elephants upon frictionless surfaces, where at the aforementioned time we are largely ignorant of the other properties of the said elephants and surfaces." It was not to be expected that a man of such stance would, only a dozen years later, be able to offer an informed assessment of The Genetical Theory, and Punnett seemed to admit every bit such: "Probably most geneticists to-day are somewhat skeptical as to the value of the mathematical treatment of their issues. With the deepest respect, and even awe, for that clan of circuitous symbols and human genius that can bring a universe to heel, they are nevertheless content to let information technology stand up at that, believing that in their own item line information technology is, after all, plodding that does it." Leonard Darwin wrote to Fisher "I am rather distressing they picked out an sometime discontinuous stick-in-the-mud like Punnett to review you in Nature. But to get 5 columns is an excellent advert. My begetter would accept been much pleased with such a review of the Origin, and merely advisedly noted the points to answer in his next edition. I think you may be well pleased. I never had so long a review" (Bennett 1983, p. 131).

In the review Punnett avant-garde his mutationist position: "Throughout the volume 1 gets the impression that Dr. Fisher views the evolutionary process equally a very gradual, most impalpable one, in spite of the discontinuous ground upon which it works." He touches on melanic moths, on poultry, and on mimicry, subjects on which he was well informed as a naturalist, and ends up by complaining about Fisher'south English. Bennett (1983, p. 35) reports that the review "was a smashing thwarting to Fisher," but one wonders whether the disappointment was more over the choice of reviewer than the content, because Fisher knew Punnett well enough not to have expected annihilation else from him. Fisher'southward response listed six points ("misstatements or other slighter misrepresentations"), and Punnett attempted to answer them. The exchange served only to emphasize the magnitude of the scientific gulf that separated the first two holders of the Arthur Balfour Professorship of Genetics.

Conclusion

Reginald Crundall Punnett owed his academic career and reputation to the good fortune of being invited past William Bateson to join him as his partner in undertaking breeding experiments in both plants and animals in the heady days that followed the rediscovery and appreciation of Mendel's article at the get-go of the 20th century. Having made a bespeak contribution to these studies his good fortune continued when he found himself the natural alternative to Bateson to occupy the Arthur Balfour Professorship of Genetics at Cambridge when Bateson declined information technology. Thereafter he lived the comfortable life of a Professor between the wars, provided with a house by the University, a Fellowship by his College, and the absence of pressing duties by either.

But 1 should not belittle the diagram that bears his name, whatsoever more than one should belittle Venn'south famous logic diagram, just because it is simple. It served a need and then well that it is difficult to see how the complex pattern of inheritance of blossom color in the sweet pea could have been unraveled without it. The discovery of partial linkage depended on the noesis thus gained. Bateson (1909, p. viii) wrote "In 1904 I had the adept fortune to gain Mr. R. C. Punnett as a partner. Since that date we have worked in close collaboration, and the piece of work that we accept thus done has been in every sense a articulation product, both as regards design, execution, and interpretation of results." But he was conscientious to attribute the diagram to Punnett, as we have noted.

G. Evelyn Hutchinson (Hutchinson 1979) remembered from his undergraduate days:

Genetics was taught twice a week, at 5 o'clock in the Michaelmas term, past R. C. Punnett … . He was a mild man with an overdominant wife who had been a major tennis player. Her opponents must take been terrified. Punnett had fine collections of Chinese porcelain and Japanese prints in a delightful house backed past an experimental garden, and he devoted himself largely to the genetics of sugariness peas. The Punnetts gave Dominicus lunches with superb wine to an incongruous set of students, one-half biological intellectuals, half athletes, all I call back men. Only almost half a dozen students took Punnett'due south grade. … The chromosome theory was still widely debated. Bateson was usually skeptical, though I know he accepted it for about a fortnight before his expiry. Punnett tended to exist more receptive to the thought. One evening the high bespeak of the form arrived unexpectedly; Punnett came in demurely and then announced that he had simply finished all the calculations of linkage of the various characters he had studied in the sugariness pea and that indeed in that location were as many linkage groups as chromosomes. The chromosome theory had worked for a plant as well as an animate being and therefore might reasonably exist expected to be of general validity (Hutchinson 1979, p. 99).

Punnett's paper reporting this is Punnett (1923b).

But I leave the terminal word to Joseph Needham (Needham 1967), the Master of Caius: "Punnett also had a highly scholarly side, existence greatly interested in the history of biology and possessing a notable library of its seventeenth and eighteenth-century literature. Unfailingly helpful and charming to younger colleagues, he would present them sometimes with rare books, and encourage them in their work in ways which they could never hope to repay. We greatly cherish his memory and record this for the information of later generations."

Acknowledgments

I am grateful to Peter O'Donald for the reference to Hutchinson (1979) and to Axel Zeitler for assistance in understanding Correns (1900).

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