'The Chromosomes in Heredity': chromosome behaviour as the physical basis of Mendel's laws

1902–1903 Life and health theory

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The claim that the behaviour of chromosomes in the maturation of the germ cells is the physical basis of Mendel's laws: pairs of chromosomes, one from the father and one from the mother, separate just as Mendelian factors do, and the pairs are distributed independently of one another. From this it was also predicted that characters lying on the same chromosome must be inherited together.

The claim was made in 1903 by the American Walter Sutton, a graduate student of Wilson's at Columbia. He studied spermatogenesis in the grasshopper Brachystola magna, whose chromosomes are large and of different sizes, and saw that they form pairs which separate during maturation. Ana Martins stresses that the cytology of those years was shaky, that Sutton revised his observations to agree with Mendel, and that the hypothesis was at first rejected by most, Morgan included.

The textbook name 'Sutton-Boveri hypothesis' she considers unfair to Sutton, since Boveri published no such hypothesis in 1902-1903.

Why this date

Two papers in the Biological Bulletin: 'On the morphology of the chromosome group in Brachystola magna', vol. 4 (December 1902), pp. 24-39, where the connection with Mendel's law is called only probable, and 'The chromosomes in heredity', vol. 4 (1903), pp. 231-251, with the full argument. The year 1903 is taken from the second paper, since according to Martins it is the first published detailed statement of the chromosome hypothesis; this also separates the work of Boveri and of Sutton by year. Bibliographic details checked against Martins's reference list and Oppenheimer's notes in the DSB. Wikidata points to the paper itself (Q42187899, an entry created from a Britannica identifier, without date or journal); the concept 'Boveri-Sutton chromosome theory' has a separate entry, Q3984080, not used here.

What it grew from

• Chromatin and mitosis: longitudinal splitting of the nuclear threads in cell division

  influenced · Confidence: medium

  The picture of division in which the nuclear threads split and separate into the daughter cells is the cytological language in which Sutton described the behaviour of chromosomes and set it beside the segregation of Mendelian factors.

  Dispute: Sutton's nearest sources on the cytology of division are Montgomery and Wilson rather than Flemming himself: Martins shows that Sutton took his interpretation of synapsis from Montgomery and that his understanding of the reduction division was still Weismannian. Flemming is the general ground here, not a direct teacher, hence the medium confidence.

  Link sources

  • William Bechtel, Andrew Bollhagen, Philosophy of Cell Biology, The Stanford Encyclopedia of Philosophy (2021) Verified 20 Sep 2026

    Flemming (1879, 1882) described in detail how the threads that he called chromatin (due to their absorption of dye), later named chromosomes, divided longitudinally, with the two halves moving apart so that one of each would end up in each daughter cell (Figure 3). Soon after researchers such as Weismann and Correns pointed to links between chromosome transmission and heredity, but it was Boveri (1902) and Sutton (1903) who provided the compelling evidence that Mendel’s factors (what would soon be called genes) are in or on chromosomes.

  • Lilian Al-Chueyr Pereira Martins, Did Sutton and Boveri propose the so-called Sutton-Boveri chromosome hypothesis?, Genetics and Molecular Biology 22 (2), 261-272 (1999) Verified 20 Sep 2026

    Sutton and other researchers of that time were strongly influenced both by cytological knowledge grounded in observations and theoretical presuppositions that led to interpretations with no observational basis.

  "Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong.

• 'Das Keimplasma': the continuity of the germ plasm and the mouse-tail experiment

  influenced · Confidence: medium

  The notion of a reduction division, which Weismann inferred on theoretical grounds, entered the cytological vocabulary and was used in 1902-1903 as given: it was on the separation of paternal and maternal chromosomes at the reduction division that Sutton and Wilson rested their explanation of the purity of the gametes.

  Dispute: Martins stresses that the Weismannian understanding of the reduction division as transverse was mistaken and that the cytology of those years hardly knew what happens at synapsis at all. Weismann therefore gave Sutton not a correct mechanism but a vocabulary and a way of posing the question; the descent is recorded as "influenced", not as a prerequisite.

  Link sources

  • Lilian Al-Chueyr Pereira Martins, Did Sutton and Boveri propose the so-called Sutton-Boveri chromosome hypothesis?, Genetics and Molecular Biology 22 (2), 261-272 (1999) Verified 20 Sep 2026

    A. Weismann had suggested that corresponding maternal and paternal chromosomes were joined by their ends in the process of fertilization, and that chromosomes were reduced to their primitive size in gametogenesis (during the so-called "reducing division").

  • Lilian Al-Chueyr Pereira Martins, Did Sutton and Boveri propose the so-called Sutton-Boveri chromosome hypothesis?, Genetics and Molecular Biology 22 (2), 261-272 (1999) Verified 20 Sep 2026

    The other would be a special division that "separates whole chromosomes by a transverse division (`reducing division' of Weismann)" (Wilson, 1902, p. 992). In other words, Wilson still interpreted meiosis in the old Weismannian sense.

  • Gloria Robinson, Weismann, August Friedrich Leopold, Complete Dictionary of Scientific Biography (1976) Verified 5 Oct 2026

    Not only did Weismann theorize that reduction division takes place, but he suggested also that a similar process to that in the maturation of the ovum could occur during spermatogenesis; this was confirmed by cytological investigation.

  "Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong.

• 'Versuche über Pflanzen-Hybriden': segregation of characters and numerical ratios

  influenced · Confidence: high

  The chromosome hypothesis was born as an attempt to put a visible mechanism under Mendel's numbers: Sutton set the behaviour of paired chromosomes in the maturation of the germ cells beside the segregation and independent assortment of Mendelian factors.

  Dispute: Martins observes that Sutton's trust in Mendel was stronger than in his own cytology: he revised his earlier observations on the separateness of the paternal and maternal sets not because of new preparations but because otherwise the recombination of characters would not come out. The influence thus ran not only from Mendel to the chromosomes but back as well, from the Mendelian scheme to what Sutton was willing to see under the microscope.

  Link sources

  • Lilian Al-Chueyr Pereira Martins, Did Sutton and Boveri propose the so-called Sutton-Boveri chromosome hypothesis?, Genetics and Molecular Biology 22 (2), 261-272 (1999) Verified 20 Sep 2026

    The "Sutton-Boveri chromosome hypothesis" attempted to establish a parallel between cytological chromosome behavior and the principles followed by Mendelian factors.

  • Jane Oppenheimer, Boveri, Theodor, Complete Dictionary of Scientific Biography, 1902 (1970) Verified 20 Sep 2026, quotation assembled from fragments

    Walter Sutton called attention to “the probability that the association of paternal and maternal chromosomes in pairs and their subsequent separation during the reduction division… may constitute the physical basis of the Mendelian law of heredity.”

  • Lilian Al-Chueyr Pereira Martins, Did Sutton and Boveri propose the so-called Sutton-Boveri chromosome hypothesis?, Genetics and Molecular Biology 22 (2), 261-272 (1999) Verified 20 Sep 2026

    If one accepts the independent segregation of chromosomes, it is possible to associate them to Mendelian factors and explain the independent segregation of characters. That was what Sutton did; he associated one factor to each chromosome (Sutton, 1903, p. 234).

  "Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong. "Assembled from fragments" means the words do not stand together on the page: we found each fragment separately and joined them with an ellipsis.

• Three papers of 1900: de Vries, Correns and Tschermak bring back Mendel's laws

  influenced · Confidence: high

  Without the rediscovery of 1900 there would have been nothing to compare with: Mendel's laws became a common subject of testing, and only two years later a cytologist began to rework his observations so as to agree with them.

  Dispute: Martins points to the nearest link: what moved Sutton was Bateson's talk in New York in September 1902, so the rediscovery acted not directly but through its English advocate.

  Link sources

  • Lilian Al-Chueyr Pereira Martins, Did Sutton and Boveri propose the so-called Sutton-Boveri chromosome hypothesis?, Genetics and Molecular Biology 22 (2), 261-272 (1999) Verified 20 Sep 2026

    Although Sutton's work was essentially cytological, he was led to distrust and review the cytological knowledge of his time, to reconcile it with the facts of heredity otherwise, it would be impossible to explain Mendel's laws. This attitude shows the strength of his reliance in Mendel's theory, only two years after its rediscovery.

  • Lilian Al-Chueyr Pereira Martins, Did Sutton and Boveri propose the so-called Sutton-Boveri chromosome hypothesis?, Genetics and Molecular Biology 22 (2), 261-272 (1999) Verified 20 Sep 2026, quotation assembled from fragments

    In 1900, Mendel's laws were "rediscovered" (Correns, 1900; Tschermak, 1900; De Vries, 1900; Stubbe, 1972; Meijer, 1985; Monaghan and Corcos, 1986). ... After the rediscovery of Mendel's work, a flood of experimental research arose to validate or disprove Mendel's principles.

  • Lilian Al-Chueyr Pereira Martins, Did Sutton and Boveri propose the so-called Sutton-Boveri chromosome hypothesis?, Genetics and Molecular Biology 22 (2), 261-272 (1999) Verified 20 Sep 2026

    It seems that, after hearing a talk delivered during September 1902 by William Bateson (1861-1926) in New York, Sutton suddenly linked his cytological knowledge to the laws of heredity (McKusick, 1960, p. 489).

  "Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong. "Assembled from fragments" means the words do not stand together on the page: we found each fragment separately and joined them with an ellipsis.

What grew out of it

• The white-eyed fly: a gene tied to a chromosome, linkage and the first genetic map

  influenced · Confidence: high

  The white-eyed fly gave the first concrete evidence for what Sutton had proposed as a hypothesis: the inheritance of a character followed the segregation of a particular chromosome. Morgan began as an opponent of the chromosome hypothesis and accepted it when he arrived at it by an independent route.

  Dispute: The link is not direct discipleship: Martins shows that Morgan rejected Sutton's hypothesis and that the rejection was well founded given the state of cytology at the time. Allen writes that what convinced Morgan was the work of Wilson and Stevens on sex chromosomes and his own experiments, not a reading of Sutton. Green speaks of a continuity of result, not of intention.

  Link sources

  • M. M. Green, 2010: A Century of Drosophila Genetics Through the Prism of the white Gene, Genetics 184 (1), 3-7 (2010) Verified 20 Sep 2026

    The result of breeding the white male to red females and additional crosses in subsequent generations led Morgan to the conclusion that the inheritance of white eye color parallels the normal meiotic segregation of the sex chromosomes in this fly. This represented the first concrete evidence that chromosomes have a role in inheritance as had been suggested nearly a decade earlier by Sutton and Boveri.

  • Garland E. Allen, Morgan, Thomas Hunt, Complete Dictionary of Scientific Biography (1974) Verified 20 Sep 2026

    Much to his credit, he rejected his skepticism about both the Mendelian and the chromosome theories when he saw from two independent lines of evidence (breeding experiments and cytology) that one could be treated in terms of the other.

  • Lilian Al-Chueyr Pereira Martins, Did Sutton and Boveri propose the so-called Sutton-Boveri chromosome hypothesis?, Genetics and Molecular Biology 22 (2), 261-272 (1999) Verified 20 Sep 2026

    For those reasons, the attitudes of those scholars who denied it, such as Thomas Hunt Morgan (Martins, 1998) or those who adopted an attitude of critical expectation, such as William Bateson (Martins, 1997 a,b) can be regarded as scientifically sound.

  "Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong.

Other links

• Boveri's multipolar mitoses: chromosomes are qualitatively different and individual

  parallel to · Confidence: medium

  Two independent approaches to one task: Boveri came from sea-urchin experiments to the qualitative difference of chromosomes, Sutton from grasshopper spermatogenesis to their correspondence with Mendelian factors. Sutton began his work independently of Boveri and himself cited Boveri's paper as his reason for publishing.

  Dispute: This is the most disputed point in the whole branch. Textbooks speak of an independent and simultaneous discovery by Sutton and Boveri, and so does Green. Martins asserts the opposite: in 1902-1903 Boveri published no chromosome hypothesis of heredity at all, he claimed priority only in 1904, and the double name was introduced by Wilson, Boveri's friend, in 1925. Oppenheimer keeps the middle ground: Sutton worked independently but published after reading Boveri's paper, so there is no pure parallel here. We record parallel as the least strained type, with this reservation.

  Link sources

  • Jane Oppenheimer, Boveri, Theodor, Complete Dictionary of Scientific Biography (1970) Verified 20 Sep 2026, quotation assembled from fragments

    The preliminary report of this investigation was published in 1902, the very year that Walter Sutton called attention to “the probability that the association of paternal and maternal chromosomes in pairs and their subsequent separation during the reduction division… may constitute the physical basis of the Mendelian law of heredity.” Although Sutton had begun his work independently of Boveri, he stated that he was publishing a description of it in 1902 because of “the appearance of Boveri’s recent remarkable paper on the analysis of the nucleus by means of observations on double-fertilized eggs.”

  • M. M. Green, 2010: A Century of Drosophila Genetics Through the Prism of the white Gene, Genetics 184 (1), 3-7 (2010) Verified 20 Sep 2026

    This represented the first concrete evidence that chromosomes have a role in inheritance as had been suggested nearly a decade earlier by Sutton and Boveri.

  • Lilian Al-Chueyr Pereira Martins, Did Sutton and Boveri propose the so-called Sutton-Boveri chromosome hypothesis?, Genetics and Molecular Biology 22 (2), 261-272 (1999) Verified 20 Sep 2026

    This name was created and advertised by Wilson (1925, p. 923). As shown above, Boveri did not publish any proposal similar to Sutton's at that time. When he declared, in 1904, that he had reached a similar conclusion at the same time as Sutton, Wilson (a friend of Boveri, to whom he dedicated all editions of his book The cell) accepted his claim and created the expression "Sutton-Boveri hypothesis" (McKusick, 1960, pp. 490-491).

  "Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong. "Assembled from fragments" means the words do not stand together on the page: we found each fragment separately and joined them with an ellipsis.

Node sources

• Lilian Al-Chueyr Pereira Martins, Did Sutton and Boveri propose the so-called Sutton-Boveri chromosome hypothesis?, Genetics and Molecular Biology 22 (2), 261-272 (1999) Verified 5 Oct 2026

  Sutton's first paper was written in October 1902. It was published in December of the same year, in the Biological Bulletin.

• Lilian Al-Chueyr Pereira Martins, Did Sutton and Boveri propose the so-called Sutton-Boveri chromosome hypothesis?, Genetics and Molecular Biology 22 (2), 261-272 (1999) Verified 5 Oct 2026

  Sutton's work of 1903 was full of difficulties, but it was much better than the brief proposals of Cannon and Wilson. We can state that he was the first to publish a detailed proposal of a chromosome hypothesis of heredity that was roughly compatible with known cytological and hereditary phenomena.

• Lilian Al-Chueyr Pereira Martins, Did Sutton and Boveri propose the so-called Sutton-Boveri chromosome hypothesis?, Genetics and Molecular Biology 22 (2), 261-272 (1999) Verified 5 Oct 2026

  "If then, the chromosomes permanently retain their individuality, it follows that all the allelomorphs represented by any one chromosome must be inherited together" (Sutton, 1903, p. 240).

• Lilian Al-Chueyr Pereira Martins, Did Sutton and Boveri propose the so-called Sutton-Boveri chromosome hypothesis?, Genetics and Molecular Biology 22 (2), 261-272 (1999) Verified 5 Oct 2026

  First of all, it seems unfair to include Boveri's name beside that of Sutton's as one of the proponents of the chromosome hypothesis of Mendelian heredity, because he did not publish any hypothesis of that kind during the relevant period (1902-1903).

• Lilian Al-Chueyr Pereira Martins, Did Sutton and Boveri propose the so-called Sutton-Boveri chromosome hypothesis?, Genetics and Molecular Biology 22 (2), 261-272 (1999) Verified 5 Oct 2026

  Sutton, W.S. (1902). On the morphology of the chromosome group in Brachystola magna. Biol. Bull. 4: 24-39. Sutton, W.S. (1903). The chromosomes in heredity. Biol. Bull. 4: 231-251.

• Frederick B. Churchill, Weismann, August Friedrich Leopold, New Dictionary of Scientific Biography (2008) Verified 5 Oct 2026

  Given his model of the germplasm, Weismann had a difficult time adjusting to the discovery of Mendel’s laws, the increasing recognition that chromosomes possessed individuality, and the demonstrations by Theodor Boveri and Walter Sutton that Mendelian factors correlated with chromosomal segregation at meiosis.

"Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong.

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