Bateson and Punnett Observe Gene Linkage Summary

  • Last updated on November 10, 2022

William Bateson and Reginald Crundall Punnett discovered that certain hereditary characters behave as if they are physically linked, adding one of the important pieces to the puzzle of heredity and the gene theory.

Summary of Event

In December, 1903, a six-year partnership began that would lead to the discovery of genetic linkage. William Bateson, a scientist studying heredity, wrote to Reginald Crundall Punnett, a fellow of Gonville and Caius College, to invite him to join his research team at Grantchester, Cambridge. The team consisted of a small group of volunteers, and their “laboratory” was the gardens and paddocks surrounding the Bateson house, along with a plot of land on the Cambridge University farm. Bateson offered Punnett the small sum of eighty pounds to join the team, all that Bateson could afford from the few small grants that he received. The letter illustrated the two extremes of the scientific endeavor: the excitement and significance of the experimental work and the severe financial restrictions that plagued Bateson for most of his career. Punnett eagerly accepted, but he refused the eighty pounds, having an income of his own. He was twenty-eight years old at the time, tolerant and friendly. Bateson was forty-two, forceful, and stern. It was a combination that engendered mutual respect. Genetics;linkage Gene linkage Linkage, genetic [kw]Bateson and Punnett Observe Gene Linkage (1906) [kw]Punnett Observe Gene Linkage, Bateson and (1906) [kw]Gene Linkage, Bateson and Punnett Observe (1906) [kw]Linkage, Bateson and Punnett Observe Gene (1906) Genetics;linkage Gene linkage Linkage, genetic [g]England;1906: Bateson and Punnett Observe Gene Linkage[01470] [c]Science and technology;1906: Bateson and Punnett Observe Gene Linkage[01470] [c]Biology;1906: Bateson and Punnett Observe Gene Linkage[01470] [c]Genetics;1906: Bateson and Punnett Observe Gene Linkage[01470] Bateson, William Punnett, Reginald Crundall

Bateson and Punnett concentrated their efforts on breeding experiments using sweet peas and poultry. They were searching for answers about laws of inheritance, such as how characters of inheritance are distributed among offspring and whether there are predictable patterns. Before they could discover linkage, they had to establish a framework of theory concerning inheritance. Bateson had formulated a number of ideas already. He was convinced that characters are inherited as discrete units and are not “blended” in the offspring, as others were proposing. He called these unit characters “allelomorphs,” a term that survives in shortened form as “alleles,” Alleles referring to individual forms of a gene. Bateson also gave the name “genetics” to the field of hereditary science.

Mendel’s law of segregation is demonstrated by an initial cross between true-breeding plants with round peas and plants with wrinkled peas. The round trait is dominant, and the wrinkled trait is recessive. The second generation consists of round-pea plants and wrinkled-pea plants produced in a ratio of 3:1.

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When Bateson and Punnett started their work, the field of genetics was in its infancy. Built on two great discoveries—Charles Darwin’s theory of evolution and Gregor Mendel’s Mendel, Gregor law of segregation—the field was still awaiting the discovery of the material of inheritance. The work that would lead to linkage was based primarily on Bateson’s fight to get Mendelism recognized. Mendel was an Austrian monk who had pursued scientific studies of peas in the gardens of the monastery in the mid-nineteenth century. With insight and patience, he discovered that characters of inheritance, such as tall or dwarf, are carried as individual packets of hereditary information. Moreover, information for traits such as tall and dwarf could be carried simultaneously in a single plant and passed on to future generations, even though the plant itself expresses only one of these traits. The expressed trait is said to be “dominant” over the unexpressed, or “recessive,” trait.

In the light of modern molecular genetics, these packets of information can be explained as being “genes.” Each trait, such as tall and dwarf, represents a different allelic form of a gene. Genes are carried on chromosomes, Chromosomes which are housed in the nucleus of each cell. Most organisms are “diploid,” carrying two complete sets of chromosomes, one set contributed by the father and the other by the mother. Alleles, therefore, exist in maternally and paternally inherited pairs. In passing the hereditary material to offspring, the organism contributes only one allele from each pair. This is the great law of segregation. When gametes (eggs and sperm) are formed, traits (alleles) for a particular character segregate from each other. A gamete thereby receives only half of the hereditary (genetic) material of the parent. At fertilization, two gametes join, combining their genetic material to make a full complement. In this way, organisms avoid doubling their hereditary material during sexual reproduction. Mendel’s work revealed this law in the absence of any knowledge of chromosomes.

Bateson’s first major victory was bringing Mendel’s work to the attention of the English-speaking world. Although Mendel had published his findings in 1866, the work had been buried in the obscure literature until 1900, when it was rediscovered independently by several scientists. As Bateson’s wife recorded the occasion in her memoirs, Bateson became aware of it as he was riding the train to London to deliver a lecture. He had taken along a copy of Mendel’s paper and read it for the first time on the train. Bateson always meticulously planned his lectures, but in this case he was so taken by Mendel’s work that he completely rewrote his presentation in order to incorporate Mendel’s studies. Upon his return home, he had Mendel’s paper translated into English and republished with footnotes, and in the following year he published a book titled Mendel’s Principles of Heredity: A Defence (1902). Mendel’s Principles of Heredity (Bateson)[Mendels Principles of Heredity] The book was, in large part, Bateson’s reaction to a fierce attack on Mendelism launched by a colleague and formerly close friend, Walter Weldon.

Ironically, after the victory with Mendelism, Bateson and Punnett, along with E. R. Saunders, Saunders, E. R. a longtime colleague of Bateson, began to accumulate data that were not in strict accordance with Mendelian principles. Mendel had demonstrated independent sorting of characters during gamete formation. If, for example, a tall plant with round seeds was also a carrier of the recessive traits of dwarf size and wrinkled seeds, the plant made gametes that carried any combination of the two traits—tall with wrinkled, dwarf with round, and so on. This independent sorting occurred only because the characters Mendel had chosen happened to be carried on separate chromosomes. It is chromosomes that sort independently during gamete formation. Characters occurring on the same chromosome, being physically linked, move together. It was this linkage behavior that Bateson, Punnett, and Saunders reported in 1906, although their interpretation did not associate heritable characters with chromosomes. In their breeding experiments with sweet peas, for example, they showed that if plants with purple flowers and long pollen grains were crossed with plants having red flowers and round pollen grains, the two characters were always passed together to the offspring. The characteristic of purple flowers was always passed with long pollen grains and red flowers with round pollen grains. Bateson and Punnett called this linkage “gametic coupling.” They were unaware that it represented physical linkage of alleles by virtue of their being carried on the same chromosome. In fact, although the chromosomal theory of inheritance Chromosomal theory of inheritance was being formulated by others at the time, Bateson remained skeptical of it throughout his career.

Bateson was the dominant figure in the Bateson-Punnett collaboration. His genius in experimentation was not in the novelty of his ideas but in his dogged attention to details. “Treasure your exceptions!” he once said in a lecture at Cambridge. “Exceptions are like the rough brickwork of a growing building which tells that there is more to come and shows where the next construction is to be.” It was this attention to exceptions that led to the discovery of linkage. Linkage would become part of the “rough brickwork” in the chromosomal theory of inheritance. It is ironic, however, that Bateson was blind to the growing building of which his own “brickwork” was a part.

Significance

It is the nature of science that data can outlive the theories to which they have been applied. In this case, Bateson and Punnett’s discovery of linkage was used by other scientists as part of the fabric of incorrect theories. Its connection with the chromosomal theory of inheritance was not immediately understood, although it can be seen now that it lent strong support to the theory. Linkage, in fact, is the manifestation of the physical connection between genes carried on the same chromosome. It helps to verify that the chromosomes are indeed the repository of the hereditary material. At the time, however, few scientists were ready to accept this theory. Even Bateson stated that the idea of particles of chromatin conferring all properties of life surpassed the rational. It was this inability to imagine hereditary material solely as particulate material that prevented the full appreciation of the implications of linkage.

The international community of scientists, in general, was divided on theories of inheritance. In France, for example, a strong preference was shown for the Lamarckian view that acquired characteristics could be passed on to offspring. In Germany, scientific sentiment resisted acceptance of the chromosome theory of heredity, preferring the claim that the cytoplasm, which lies outside the nucleus, played the vital role in inheritance. In Denmark, the famous botanist Wilhelm Ludvig Johannsen, Johannsen, Wilhelm Ludvig who rejected Lamarckian views and coined the term “gene,” was unwilling to consider that the gene might correspond to particulate matter in the chromosome. An American scientist, Thomas Hunt Morgan, Morgan, Thomas Hunt was the major proponent of the chromosomal theory of inheritance, showing in 1910 that the behavior of chromosomes obeyed the law of segregation and could explain linkage. Yet Morgan was slow to accept Mendelism. Bateson did not accept Morgan’s chromosome theory until 1921, when, after visiting Morgan’s laboratory, Bateson gave it tentative acceptance, only to return to his criticism in his last paper in 1926. The certainty of the connections among Mendel’s principles, linkage, and the chromosomes would not come until 1953, when James D. Watson and Francis Crick finally broke the genetic code.

Bateson was fully cognizant of the advantages his work could have for agriculture. Agriculture;planned breeding of crops If characters within a population could be manipulated through planned breeding, then superior hybrids of cash crops could be produced. Bateson worked hard to convince the English government that this type of research should be supported with government funds. He even developed a strain of sugar beet that would not bolt early and a strain of flax that contained especially long fibers. Government policies did shift, and this marked the beginning of the government’s taking an active role in support of scientific research.

The unraveling of genetic theory also helped to establish the study of eugenics, Eugenics the manipulation of genes in human populations. Even Bateson, although he never advocated applying eugenics, wondered what biologists would do with the knowledge. He wondered if it could help to produce “healthier, wiser, or more worthy” people. It took the application of eugenics in the horrific experiments of Nazi Germany to still enthusiasm for the idea. That was ample warning that the field of genetics—the science named by Bateson—must never be used to manipulate the genes within a human population through selective breeding. Genetics;linkage Gene linkage Linkage, genetic

Further Reading
  • citation-type="booksimple"

    xlink:type="simple">Bateson, Beatrice. William Bateson, F.R.S. Naturalist. Cambridge, England: Cambridge University Press, 1928. A memoir by William Bateson’s wife, written after his death. Includes a number of Bateson’s letters and lectures, with commentary by the author.
  • citation-type="booksimple"

    xlink:type="simple">Bateson, William, E. R. Saunders, and Reginald Crundall Punnett. “Experimental Studies in the Physiology of Heredity.” Reports to the Evolution Committee of the Royal Society, Report III (1906): 1-53. This is the original paper announcing the discovery of linkage. Its long columns of data are testimony to the changes that have occurred in science publishing. Today, journal articles normally include only summarizing graphs and charts of original data. Also, a “Miss” or “Mrs.” was required to identify any woman author; therefore, the second author is identified as “Miss” E. R. Saunders in this paper. Interesting reading for those who seek information on the history of genetics.
  • citation-type="booksimple"

    xlink:type="simple">Bowler, Peter J. The Mendelian Revolution: The Emergence of Hereditarian Concepts in Modern Science and Society. Baltimore: The Johns Hopkins University Press, 1989. Documents the importance of Mendelian genetics after 1900 as well as the social and scientific impacts of the rediscovery of Mendel’s work. Provides good background information for an appreciation of Mendelian genetics. Includes an extensive bibliography.
  • citation-type="booksimple"

    xlink:type="simple">Carlson, Elof Axel. Mendel’s Legacy: The Origin of Classical Genetics. Cold Spring Harbor, N.Y.: Cold Spring Harbor Laboratory Press, 2004. Based heavily on early twentieth century sources, this book traces the roots of genetics in breeding analysis and studies of cytology, evolution, and reproductive biology. Highly illustrated.
  • citation-type="booksimple"

    xlink:type="simple">Cock, A. G. “William Bateson, Mendelism, and Biometry.” Journal of the History of Biology 6 (1973): 1-36. The main body of this article is fairly technical, but an appended section describes the experimental notebooks of Bateson and Punnett, with photographs of selected pages, including several on which Bateson and Punnett scribbled in the margins wagers they had made on the outcome of certain experiments.
  • citation-type="booksimple"

    xlink:type="simple">Crowther, J. G. British Scientists of the Twentieth Century. London: Routledge & Kegan Paul, 1952. Includes a very readable chapter on Bateson’s life. Discusses Bateson’s scientific work in nontechnical terms, including the discovery with Punnett of linkage.
  • citation-type="booksimple"

    xlink:type="simple">Dunn, L. C. A Short History of Genetics: The Development of Some of the Main Lines of Thought, 1864-1939. 1965. Reprint. Ames: Iowa State University Press, 1991. Summarizes the general history of theories of heredity and places Bateson and Punnett’s work in context. Includes a glossary and a bibliography of both primary and secondary sources.
  • citation-type="booksimple"

    xlink:type="simple">Kevles, Daniel. “Genetics in the United States and Great Britain, 1890-1930.” Isis 71 (1980): 441-455. Provides an excellent summary of Bateson’s professional career and his influence on scientific thought in England and the United States.
  • citation-type="booksimple"

    xlink:type="simple">Mayr, Ernst. The Growth of Biological Thought: Diversity, Evolution, and Inheritance. Cambridge, Mass.: Harvard University Press, 1982. A monumental work on the history of genetics and evolution. Mayr is a world-famous expert in the field, and his thought-provoking prose is as stimulating to the professional in the field as it is accessible to the average reader. Includes a full set of references and an excellent index. Considered a classic in biology.
  • citation-type="booksimple"

    xlink:type="simple">Punnett, Reginald Crundall. “Early Days of Genetics.” Heredity 4 (April, 1950): 1-10. This was an address delivered at the one hundredth meeting of the Genetical Society in Cambridge, England, on June 30, 1949. It is a delightful account of Punnett’s collaborative work with Bateson, with details that reveal the personalities of the two men and the daily routines of their work.
  • citation-type="booksimple"

    xlink:type="simple">Rothwell, Norman V. Understanding Genetics. 4th ed. New York: Oxford University Press, 1988. A well-written college text that discusses genetics in general, allowing the reader to put linkage into context. Includes an extensive glossary, problem sets with answers, numerous diagrams and photographs, and chapter bibliographies.
  • citation-type="booksimple"

    xlink:type="simple">Sturtevant, A. H. A History of Genetics. 1965. Reprint. Cold Spring Harbor, N.Y.: Cold Spring Harbor Laboratory Press, 2001. Summarizes general theories of heredity and helps put Bateson and Punnett’s work into context.

Bateson Publishes Mendel’s Principles of Heredity

Sutton Proposes That Chromosomes Carry Hereditary Traits

Punnett’s Mendelism Includes Diagrams Showing Heredity

Hardy and Weinberg Present a Model of Population Genetics

Morgan Develops the Gene-Chromosome Theory

Johannsen Coins the Terms “Gene,” “Genotype,” and “Phenotype”

Sturtevant Produces the First Chromosome Map

Categories: History Content