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  • 1. Copyright  2003 by the Genetics Society of America Perspectives Anecdotal, Historical and Critical Commentaries on Genetics Edited by James F. Crow and William F. Dove C. C. Tan: A Life of Peaks and Valleys James F. Crow Laboratory of Genetics, University of Wisconsin, Madison, Wisconsin 53706 I first met C. C. Tan (Tan Jiazhen) in 1946 at the University of Texas in Austin where I was visiting at the time. He was there to give a seminar on “mosaic of the spots if they do occur. The penetrance and size of spots are greater at lower developmental temperatures. The other 11 alleles produce a much larger amount dominance” in ladybird (aka ladybug) beetles. I was of black pigment, which may cover almost all the elytron, particularly interested because of the similarity to the and the location of the black pigment is constant for a pattern expression of scute alleles in Drosophila melanogas- particular allele. Each of these alleles is dominant to ter and was eager to talk to him about this and about s, and each acts independently of the others. Thus, his D. pseudoobscura work with Dobzhansky and Sturte- heterozygotes for two different dominant alleles are vant. So we arranged to have dinner together. We went black in all areas that would be black in either of the by trolley to a Chinese restaurant, Sam Wah’s, which I two constituent homozygotes. Tan (1946a) called this believe was the only one in Austin. He suggested that mosaic dominance. The yellow areas are conditioned he order the food, since by speaking in the native lan- by the s allele. They may or not show small spots, de- guage he could get us more authentic Chinese dishes. pending strongly on the developmental temperature. Alas, the waiter did not speak Chinese; his ancestors When the beetle emerges from the pupa, the entire had emigrated several generations earlier. He sum- elytron is yellow. The black pigment then appears gradu- moned the cook, who it turned out didn’t speak Chinese ally, starting at the edges. The sharp delineation of the either, nor English for that matter. I ended up ordering pigmented areas, the independence of the individual the food. A little over half a century later, Tan and I alleles, the timing of the developmental pattern, and met again, this time in China. Of course he recalled the effect of temperature made this promising material the incident, and we relived an amusing episode. A lot for the study of developmental patterns, and the work had happened in the meantime, especially to him. attracted a great deal of attention at the time. One The pigment pattern of the ladybird elytra (hard wing hypothesis, introduced by Dubinin and Serebrovsky covers, singular elytron) is remarkably polymorphic; dif- (Dubinin 1933) to explain mosaic dominance of the ferent geographical regions show characteristic pattern scute and achaete alleles in Drosophila, was called “step frequencies (Tan 1946a). More than 200 forms had allelomorphism.” The idea was that the bristle patterns been identified by 1946. The differences in various geo- reflected subdivisions of the gene. But the sub-gene graphical regions are so striking that classical entomolo- hypothesis created more problems than it solved (Stur- gists had often classified them as separate species, even tevant and Schultz 1931), so most of the discussion separate genera. Tan found that the entire range of at the time concerned developmental patterns rather patterns could be explained by variation at a single than domains within genes. autosomal locus with 12 alleles. Hoshino (1940) had C. C. Tan was born in Zhejiang Province in China studied three additional alleles not found in the regions in 1909 and did his undergraduate work at Soochow Tan studied, which fit into the explanation, so there University. (Soochow was known as “the Chinese Ven- were 15 alleles altogether and undoubtedly more to be ice.”) Tan then did graduate work at Yenching Univer- discovered. sity in Peking where two of the faculty, Ju Chi Li and One allele, s (for succinea), is recessive to the others. T. Y. Chen, had been students in T. H. Morgan’s labora- It produces a background orange-yellow color, which tory at Columbia University. Li carried out several cyto- may or may not have a number of dark spots. The logical and genetic studies while in the Morgan lab (e.g., location of spots is very specific; they may occur at any Bridges et al. 1936). Also, he had played football at of 10 sites. The penetrance of s is variable, as is the size Purdue University. I visited him in his office in Beijing Genetics 164: 1–4 (May 2003)
  • 2. 2 J. F. Crow assigned the task of making a cytological map of the chromosomes of D. pseudoobscura. He quickly became an expert and soon found that races A and B, as they were then called, differed by a large number of easily recognized inversions. (A and B are now called D. pseudo- obscura and D. persimilis.) The inversions were so charac- teristic that they could be used as identifying markers for the two species, which are almost indistinguishable by external morphology (Tan 1935). Tan’s work grabbed the enthusiastic attention of Sturtevant and Dobzhan- sky, and they began immediately to study the geographi- cal distribution of the various inversion types. This marked the exciting beginning of the great Sturtevant– Dobzhansky collaboration, which continued until grad- ually the two had a falling out and Dobzhansky moved to Columbia University. (For speculation as to the causes of the rift, see Provine 1981.) One notable result of this work was the use of overlapping inversions to infer the phylogeny of the different chromosome types. Tan also pioneered in studying the genetic basis of sexual isolation (Dobzhansky and Tan 1936; Tan 1946b). This work, and much more, was summarized in Dobz- hansky’s (1937) Genetics and the Origin of Species, which became an instant classic. I vividly recall my excitement as a graduate student on first reading this book in early 1938. I thought it was the greatest thing since Darwin. Among the discoveries at the time was a new species, Drosophila miranda (Dobzhansky and Tan 1936). For one thing, this species had a number of chromosomal inversions, including those of a hypothetical form ances- tral to or intermediate between a series of pseudoobscura and persimilis inversion classes. Tan estimated that at least 49 chromosome breaks were required to explain all the differences between miranda and the others. More Two views of C. C. Tan. The photographs were taken during interesting, as a result of a translocation, an autosomal a visit to the University of Wisconsin in 1986. Included in the arm split off and was inherited solely in males. Thus, it photographs are Seymour Abrahamson and Rayla Greenberg behaved like a Y chromosome. This neo-Y, because of Temin. the absence of recombination in Drosophila males, was expected to degenerate. There was much speculation when he was nearly 90. He was still large and robust, at the time as to why and how rapidly such degeneration regularly rode a bicycle to work, and was eager to talk would occur, but the kind of detailed analysis that can about either genetics or athletics. He became Tan’s provide answers has been possible only recently (e.g., mentor for research on ladybird beetles, which led to Bachtrog and Charlesworth 2002). a master’s thesis. Li was so pleased with this work that Tan continued to collaborate on evolutionary studies he sent the resulting paper to Morgan, who by this with Sturtevant and Dobzhansky (Dobzhansky and Tan time had moved to CalTech in Pasadena. Fortuitously, 1936; Sturtevant and Tan 1937) and on develop- Dobzhansky had worked with ladybirds in Russia, so mental subjects with others (Tan and Poulson 1937; Morgan naturally passed the manuscript on to him. Gottschewski and Tan 1938). He was highly produc- Dobzhansky thought highly of it, and after some revision tive during his time in the United States, and he contin- and editing by the Morgan group, the paper was pub- ued this on his return to China. In 1937 he joined the lished in the United States (Tan and Li 1934). faculty of Chekiang University, which, because of the On Dobzhansky’s recommendation, Morgan invited Japanese incursions, had been moved to a southwestern Tan to CalTech for Ph.D. work. He arrived in 1934 and locale in Kweichow. During that time, Tan had support immediately began work with Dobzhansky and Sturte- from the Rockefeller Foundation. Although he contin- vant, becoming Dobzhansky’s first Ph.D. student. The ued some Drosophila studies, his main emphasis re- enormous power of giant salivary chromosomes of Dro- turned to ladybird beetles. In addition to his work on sophila had recently become apparent, and Tan was mosaic dominance, he and his students performed
  • 3. Perspectives 3 large-scale studies on the racial variation and population But life was not good, and he was under great social structure. This was an exciting period for Chinese genet- pressure to conform. His wife, who had lived in the ics and for Tan, who by this time had a worldwide reputa- United States, was particularly unhappy. The Li family tion. He also monitored a number of students. Among eventually contrived, despite hardships, to get out of them was T. C. Hsu, later to become famous for his China through Hong Kong. [As a poignant aside, I note happy discovery that treatment with a hypotonic salt that Li’s book was dedicated “to Jeff.” I often wondered solution makes individual human chromosomes much who Jeff was. Later I learned (Spiess 1983): Jeffrey was more distinct. This finding was important in ushering an infant son who died during the hardships of the Li in the renaissance of human cytology, which flourished family’s last days in China.] in the late 1950s. The Rockefeller Foundation also sup- In the United States, largely through the influence ported Tan for a return to the United States to consoli- of H. J. Muller, Li accepted a position at the University date his studies and write them up for publication (Tan of Pittsburgh, where he has been ever since—a decision 1946a,b). It was during this period that I saw him in neither he nor Pittsburgh has reason to regret. His repu- Texas. tation as a teacher continued to grow throughout the Returning to China in 1946, he made another trip world. His book quickly became popular in the United abroad, in 1948. He was a member of the standing States and went through several editions. He is held in council of the 8th International Congress of Genetics, great admiration and affection, and recently celebrated which met that year in Sweden. Alas, the Lysenko deba- his 90th birthday. cle in the Soviet world was taking hold in China. For the During the period from about 1958 to 1966, the Ly- next 3 decades, Tan’s life was one of political upheaval, senkoist and Mendelian views of genetics were permit- intellectual uncertainty, and personal hardship, mixed ted to coexist. That must have been terribly confusing with shorter periods in which things went somewhat for students. “Practical” research was permitted, and better. At no time, however, was he able to pursue the Tan wrote several papers on the effects of high-energy research he was really interested in. radiation on the chromosomes of the rhesus monkey. During this period in China, orthodox geneticists Tan described an incident from that time, which is were forced to conform to Lysenko’s Lamarckian views revealing and also wryly amusing. An experimenter had or else switch to another field. Maize geneticists told treated cotton with a vital dye and reported inherited me of being sent to grow maize in cold climates, where effects of the treatment in the next generation. Tan was the short growing season was totally unsuited. Not only sent to investigate and later discovered that a paper were these workers predictably unsuccessful, they en- reporting these results had been submitted with his dured various hardships including malnutrition. Tan name attached. He adroitly explained, however, that he stopped teaching genetics and concentrated on evolu- had tried to learn the techniques but had been unsuc- tion. He escaped political difficulties by emphasizing cessful. Since he had not adequately mastered the tech- paleontology and the evidence of evolution, rather than niques, he did not deserve to be an author. So his name mechanisms. Of course, the ladybird and Drosophila was removed, and his reputation among Mendelian ge- population studies had to be dropped; they were not neticists was thereby preserved. “practical” enough. Then another blow fell. The period 1966–1976 was The popularity of Lysenkoism is not hard to under- the time of the Cultural Revolution, “ten long years.” stand. It promised quick results without the necessity of Again, these were hard times, and Tan published almost learning the complicated rules of statistics, Mendelism, nothing during that period. Furthermore, he lost almost meiosis, linkage, and cytogenetics. And sometimes it all contact with his colleagues abroad. Finally, in 1978 was successful, since selecting the best individuals to use he was able to leave China and attend the 50th anniver- as parents works for various systems of inheritance. But sary of the founding of CalTech’s Biology Division in such techniques as inbreeding and hybridization for Pasadena. corn breeding did not fit the orthodoxy. I think Soviet At last, in 1979 at the age of 70 when most people and Chinese agriculture lost some momentum for an- are retired, he was able again to do genetic research. other reason: since R. A. Fisher was discredited as a Once more, he took up his study of ladybird beetles, Mendelist, his efficient experimental designs for field finding more alleles and obtaining more population crops were not followed. Many Chinese geneticists and data. But this was no longer center stage. The molecular breeders were trained in Russia. Followers of Mendel revolution had occurred during the eclipse of Chinese and Morgan had a bad time. genetics, and genetics was going in new directions. Char- Among the Mendelists was the population geneticist, acteristically, Tan immediately became the leader. He C. C. Li, who had a growing reputation as a teacher and was active in the search for harmful environmental textbook writer. Several Chinese geneticists, whom I saw chemicals, advocating the Ames system for testing possi- years later, remembered him and extolled his great skill ble mutagens and carcinogens. He was alert to molecu- as a teacher. His widely influential book (Li 1948) was lar techniques and wrote about RNA amplification in beginning to catch on, both inside and outside China. heterosis. He wrote a number of essays and review arti-
  • 4. 4 J. F. Crow cles on various aspects of genetics and evolution and book is a wonderful way to see the breadth of his interest. the changes brought about by technical advances. He Now, well into his nineties, he can look back on a career was an early advocate of the construction of a human that has had far higher peaks and deeper valleys than genome library. He directed various studies on rice. He most geneticists can claim. Despite hardships and set- used mitochondrial DNA to study human variability. backs, he has had a rich life. He has lived by his intellect And much more. In his 70 years of teaching and re- and personality, and by his wits, both scientifically and search, despite the long interruptions, he has published politically. The Selected Works of Tan Jaizhen shows the more than 100 scientific papers—original research, re- fruits. views, translations, and essays. His overview of Chinese I am indebted to Joshua Lederberg and Rayla Temin for reading genetics (Fu et al. 1995) is a concise summary of a long the manuscript and offering useful suggestions. history. As early as 1952, Tan had moved to Shanghai to be- come Professor and Chairman of the Biology Depart- LITERATURE CITED ment at Fudan University. He has remained there since, Bachtrog, D., and B. Charlesworth, 2002 Reduced adaptation holding various high administrative positions. Now re- of a non-recombining neo-Y chromosome. Nature 416: 323–326. Bridges, C. B., E. N. Skoog and J. C. Li, 1936 Genetic and cytological tired, he is honorary director of the Genetics Institute studies of a deficiency (notopleural) in the second chromosome at that university. of Drosophila melanogaster. Genetics 21: 788–795. In the 1980s and 90s the world of genetics in China Dobzhansky, Th., 1937 Genetics and the Origin of Species. Columbia University Press, New York. made up for its neglect of Tan. He was showered with Dobzhansky, Th., and C. C. Tan, 1936 Studies on hybrid sterility. richly deserved honors. These are too numerous to list, III. A comparison of the chromosome structure in two related but I shall mention a few. He was president of the Genet- species, Drosophila pseudoobscura and Drosophila miranda. Zeit. in- dukt. Abstammungs.-Vererbungsl. 72: 88–113. ics Society of China, the Environmental Mutagens Soci- Dubinin, N. P., 1933 Step-allelomorphism in Drosophila melanogaster. ety of China, and the Biotechnology Society of China. J. Genet. 27: 443–464. He was an officer, usually vice president, of the Interna- Fu, J. L., E. H. Chu and J. Z. Tan, 1995 Perspectives on genetics in China. Annu. Rev. Genet. 29: 1–18. tional Genetics Congress in 1948, 1983, 1988, and 1993. Gottschewski, G., and C. C. Tan, 1938 The homology of the eye Finally, he was the major proponent and then president color genes in Drosophila melanogaster and Drosophila pseudoobscura of the 18th International Congress, held in Beijing in as determined by transplantation. II. Genetics 23: 221–238. Hoshino, Y., 1940 Genetical studies on the pattern types of the lady- 1998. Among his foreign honors are a distinguished bird beetle, Harmonia axyridis Pallas. J. Genet. 40: 215–228. alumni award from the California Institute of Technol- Li, C. C., 1948 An Introduction to Population Genetics. National Peking ogy, foreign membership in the United States National University Press, Peking. Provine, W. B., 1981 Origins of the genetics of natural populations Academy of Sciences, foreign membership in the Japa- series, pp. 5–83 in Dobzhansky’s Genetics of Natural Populations nese and British Genetics Societies, and honorary life I–XLIII, edited by R. C. Lewontin, J. A. Moore, W. B. Provine and B. Wallace. Columbia University Press, New York. member of the New York Academy of Sciences. Finally, Spiess, E., 1983 Chung Chun Li, courageous scholar of population in 1999 he received a unique honor: a planet was named genetics, human genetics, and biostatistics: a living essay. Am. J. after him, Planet Number 3542, discovered at an obser- Hum. Genet. 16: 603–630. Sturtevant, A. H., and J. Schultz, 1931 The inadequacy of the vatory of the Chinese Academy of Sciences. What other sub-gene hypothesis of the nature of the scute allelomorphs of geneticist can claim this? Drosophila. Proc. Natl. Acad. Sci. USA 17: 265–270. Tan’s volume, The Selected Works of Tan Jaizhen (Tan Sturtevant, A. H., and C. C. Tan, 1937 The comparative genetics of Drosophila pseudoobscura and Drosophila melanogaster. J. Genet. 1992), is a trove of interesting items, especially for those 34: 415–432. who can read Chinese. But pictures are the same in any Tan, C. C., 1935 Salivary gland chromosomes in the two races of language, and the book has some 45 pages of them, Drosophila pseudoobscura. Genetics 20: 473–490. Tan, C. C., 1946a Mosaic dominance in the inheritance of color mostly in color, showing the gregarious Tan at various patterns in the lady-bird beetle, Harmonia axyridis. Genetics 31: times of his life, along with almost a Who’s Who of geneti- 195–210. Tan, C. C., 1946b Genetics of sexual isolation between Drosophila cists that he met during his travels. The pictures repre- pseudoobscura and Drosophila persimilis. Genetics 31: 558–573. sent two periods, with large gaps caused by Lysenkoism Tan, C. C., 1992 The Selected Works of Tan Jiazhen. Zhejiang Science and the Cultural Revolution. The book is composed of and Technology Publishing House, Hangzhou, China (in Chinese and English). a summary and sometimes the entire text of some 80 Tan, C. C., and J. C. Li, 1934 Inheritance of the elytral color patterns papers. The majority of the articles are in Chinese, but of the lady-bird beetles, Harmonis axyridis Pall. Am. Nat. 68: 262– enough are in English to satisfy the language chal- 265. Tan, C. C., and D. F. Poulson, 1937 The behavior of vermilion and lenged. Included is a heart-warming tribute to his men- orange eye colors in transplantation in Drosophila pseudoobscura. tor, Dobzhansky, whom Tan never saw after 1948. This J. Genet. 34: 433–435.