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Home > Dictionary of Science Quotations > Scientist Names Index M > Gregor Mendel Quotes

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Gregor Mendel
(22 Jul 1822 - 6 Jan 1884)

Austrian botanist, geneticist and monk.

Science Quotes by Gregor Mendel (7 quotes)

Experiments on ornamental plants undertaken in previous years had proven that, as a rule, hybrids do not represent the form exactly intermediate between the parental strains. Although the intermediate form of some of the more striking traits, such as those relating to shape and size of leaves, pubescence of individual parts, and so forth, is indeed nearly always seen, in other cases one of the two parental traits is so preponderant that it is difficult or quite impossible, to detect the other in the hybrid. The same is true for Pisum hybrids. Each of the seven hybrid traits either resembles so closely one of the two parental traits that the other escapes detection, or is so similar to it that no certain distinction can be made. This is of great importance to the definition and classification of the forms in which the offspring of hybrids appear. In the following discussion those traits that pass into hybrid association entirely or almost entirely unchanged, thus themselves representing the traits of the hybrid, are termed dominating and those that become latent in the association, recessive. The word 'recessive' was chosen because the traits so designated recede or disappear entirely in the hybrids, but reappear unchanged in their progeny, as will be demonstrated later.
— Gregor Mendel
'Experiments on Plant Hybrids' (1865). In Curt Stern and Eva R. Sherwood (eds.), The Origin of Genetics: A Mendel Source Book (1966), 9.
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If A denotes one of the two constant traits, for example, the dominating one, a the recessive, and the Aa the hybrid form in which both are united, then the expression:
A + 2Aa + a
gives the series for the progeny of plants hybrid in a pair of differing traits.
— Gregor Mendel
'Experiments on Plant Hybrids' (1865). In Curt Stem and Eva R. Sherwood (eds.), The Origin of Genetics: A Mendel Source Book (1966), 16.
Science quotes on:  |  Dominant (14)  |  Expression (110)  |  Genetics (101)  |  Hybrid (12)  |  Recessive (3)  |  Trait (22)

In this generation, along with the dominating traits, the recessive ones also reappear, their individuality fully revealed, and they do so in the decisively expressed average proportion of 3:1, so that among each four plants of this generation three receive the dominating and one the recessive characteristic.
— Gregor Mendel
'Experiments on Plant Hybrids' (1865). In Curt Stern and Eva R. Sherwood (eds.), The Origin of Genetics: A Mendel Source Book (1966), 10.
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My experiments with single traits all lead to the same result: that from the seeds of hybrids, plants are obtained half of which in turn carry the hybrid trait (Aa), the other half, however, receive the parental traits A and a in equal amounts. Thus, on the average, among four plants two have the hybrid trait Aa, one the parental trait A, and the other the parental trait a. Therefore, 2Aa+ A +a or A + 2Aa + a is the empirical simple series for two differing traits.
— Gregor Mendel
Letter to Carl Nδgeli, 31 Dec 1866. In Curt Stern and Eva R. Sherwood (eds.), The Origin of Genetics: A Mendel Source Book (1966), 63.
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That no generally applicable law of the formulation and development of hybrids has yet been successfully formulated can hardly astonish anyone who is acquainted with the extent of the task and who can appreciate the difficulties with which experiments of this kind have to contend.
— Gregor Mendel
'Experiments on Plant Hybrids' (1865). In Curt Stern and Eva R. Sherwood (eds.), The Origin of Genetics: A Mendel Source Book (1966), 2.
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The theory is confirmed that pea hybrids form egg and pollen cells, which, in their constitution, represent in equal numbers all constant forms which result for the combination of the characters united in fertilization.
— Gregor Mendel
As collected in Forest Ray Moulton (ed.), The Autobiography of Science (1945), 586.
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When two plants, constantly different in one or several traits, are crossed, the traits they have in common are transmitted unchanged to the hybrids and their progeny, as numerous experiments have proven; a pair of differing traits, on the other hand, are united in the hybrid to form a new trait, which usually is subject to changes in the hybrids' progeny.
— Gregor Mendel
'Experiments on Plant Hybrids' (1865). In Curt Stern and Eva R. Sherwood (eds.), The Origin of Genetics: A Mendel Source Book (1966), 5.
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Quotes by others about Gregor Mendel (14)

A moment's consideration of this case shows what a really great advance in the theory and practise of breeding has been obtained through the discovery of Mendel's law. What a puzzle this case would have presented to the biologist ten years ago! Agouti crossed with chocolate gives in the second filial generation (not in the first) four varieties, viz., agouti, chocolate, black and cinnamon. We could only have shaken our heads and looked wise (or skeptical).
Then we had no explanation to offer for such occurrences other than the 'instability of color characters under domestication,' the 'effects of inbreeding,' 'maternal impressions.' Serious consideration would have been given to the proximity of cages containing both black and cinnamon-agouti mice.
Now we have a simple, rational explanation, which anyone can put to the test. We are able to predict the production of new varieties, and to produce them.
We must not, of course, in our exuberance, conclude that the powers of the hybridizer know no limits. The result under consideration consists, after all, only in the making of new combinations of unit characters, but it is much to know that these units exist and that all conceivable combinations of them are ordinarily capable of production. This valuable knowledge we owe to the discoverer and to the rediscoverers of Mendel's law.
'New Colour Variety of the Guinea Pig', Science, 1908, 28, 250-252.
Science quotes on:  |  Heredity (53)  |  Hybrid (12)  |  Mouse (26)

The foundations of population genetics were laid chiefly by mathematical deduction from basic premises contained in the works of Mendel and Morgan and their followers. Haldane, Wright, and Fisher are the pioneers of population genetics whose main research equipment was paper and ink rather than microscopes, experimental fields, Drosophila bottles, or mouse cages. Theirs is theoretical biology at its best, and it has provided a guiding light for rigorous quantitative experimentation and observation.
'A Review of Some Fundamental Concepts and Problems of Population Genetics', Cold Spring Harbor Symposia on Quantitative Biology, 1955, 20, 13-14.
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When... the biologist is confronted with the fact that in the organism the parts are so adapted to each other as to give rise to a harmonious whole; and that the organisms are endowed with structures and instincts calculated to prolong their life and perpetuate their race, doubts as to the adequacy of a purely physiochemical viewpoint in biology may arise. The difficulties besetting the biologist in this problem have been rather increased than diminished by the discovery of Mendelian heredity, according to which each character is transmitted independently of any other character. Since the number of Mendelian characters in each organism is large, the possibility must be faced that the organism is merely a mosaic of independent hereditary characters. If this be the case the question arises: What moulds these independent characters into a harmonious whole? The vitalist settles this question by assuming the existence of a pre-established design for each organism and of a guiding 'force' or 'principle' which directs the working out of this design. Such assumptions remove the problem of accounting for the harmonious character of the organism from the field of physics or chemistry. The theory of natural selection invokes neither design nor purpose, but it is incomplete since it disregards the physiochemical constitution of living matter about which little was known until recently.
The Organism as a Whole: From a Physiochemical Viewpoint (1916), v-vi.
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I have watched all the work going on there, and the more I see of it the more I am convinced that Mendelism has nothing to do with evolution.
Letter, 'Embryology and Evolution,' Nature (1931), 127, 56.
Science quotes on:  |  Evolution (535)

The fundamental biological variant is DNA. That is why Mendel's definition of the gene as the unvarying bearer of hereditary traits, its chemical identification by Avery (confirmed by Hershey), and the elucidation by Watson and Crick of the structural basis of its replicative invariance, are without any doubt the most important discoveries ever made in biology. To this must be added the theory of natural selection, whose certainty and full significance were established only by those later theories.
In Jacques Monod and Austryn Wainhouse (trans.), Chance and Necessity: An Essay on the Natural Philosophy of Modern Biology (1971), 104.
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In the modern interpretation of Mendelism, facts are being transformed into factors at a rapid rate. If one factor will not explain the facts, then two are involved; if two prove insufficient, three will sometimes work out. The superior jugglery sometimes necessary to account for the results may blind us, if taken too naively, to the common-place that the results are often so excellently 'explained' because the explanation was invented to explain them. We work backwards from the facts to the factors, and then, presto! explain the facts by the very factors that we invented to account for them. I am not unappreciative of the distinct advantages that this method has in handling the facts. I realize how valuable it has been to us to be able to marshal our results under a few simple assumptions, yet I cannot but fear that we are rapidly developing a sort of Mendelian ritual by which to explain the extraordinary facts of alternative inheritance. So long as we do not lose sight of the purely arbitrary and formal nature of our formulae, little harm will be done; and it is only fair to state that those who are doing the actual work of progress along Mendelian lines are aware of the hypothetical nature of the factor-assumption.
'What are 'Factors' in Mendelian Explanations?', American Breeders Association (1909), 5, 365.
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Certain students of genetics inferred that the Mendelian units responsible for the selected character were genes producing only a single effect. This was careless logic. It took a good deal of hammering to get rid of this erroneous idea. As facts accumulated it became evident that each gene produces not a single effect, but in some cases a multitude of effects on the characters of the individual. It is true that in most genetic work only one of these character-effects is selected for study—the one that is most sharply defined and separable from its contrasted character—but in most cases minor differences also are recognizable that are just as much the product of the same gene as is the major effect.
'The Relation of Genetics to Physiology and Medicine', Nobel Lecture (4 Jun 1934). In Nobel Lectures, Physiology or Medicine 1922-1941 (1965), 317.
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It was not noisy prejudice that caused the work of Mendel to lie dead for thirty years, but the sheer inability of contemporary opinion to distinguish between a new idea and nonsense.
In 'The Commemoration of Great Men', British Medical Journal (20 Feb 1932). In The Adelphi (1932), 4, 480, and in The Collected Papers of Wilfred Trotter, FRS (1941), 27.
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There is nothing opposed in Biometry and Mendelism. Your husband [W.F.R. Weldon] and I worked that out at Peppards [on the Chilterns] and you will see it referred in the Biometrika memoir. The Mendelian formula leads up to the “ancestral law.” What we fought against was the slovenliness in applying Mendel's categories and asserting that such formulae apply in cases when they did not.
Letter to Mrs.Weldon (12 Apr 1907). Quoted in M. E. Magnello, 'Karl Pearson's Mathematization of Inheritance: From Ancestral Heredity to Mendelian Genetics (1895-1909)', Annals of Science (1998), 55, 89.
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I may finally call attention to the probability that the association of paternal and maternal chromosomes in pairs and their subsequent separation during the reducing division as indicated above may constitute the physical basis of the Mendelian law of heredity.
'On the Morphology of the Chromosome Group in Brachystola Magna', Biological Bulletin (1902), 4, 39.
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If a given scientist had not made a given discovery, someone else would have done so a little later. Johann Mendel dies unknown after having discovered the laws of heredity: thirty-five years later, three men rediscover them. But the book that is not written will never be written. The premature death of a great scientist delays humanity; that of a great writer deprives it.
Pensιes d'un Biologiste (1939). Translated in The Substance of Man (1962), 89.
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I kind of like scientists, in a funny way. … I'm kind of interested in genetics though. I think I would have liked to have met Gregor Mendel. Because he was a monk who just sort of figured this stuff out on his own. That's a higher mind, that’s a mind that's connected. … But I would like to know about Mendel, because I remember going to the Philippines and thinking “this is like Mendel’s garden” because it had been invaded by so many different countries over the years, and you could see the children shared the genetic traits of all their invaders over the years, and it made for this beautiful varietal garden.
Answering question: “If you could go back in time and have a conversation with one person, who would it be and why?” by Anniedog03 during an Internet Reddit AMA (Ask Me Anything) online session (17 Jan 2014).
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I have attempted to form a judgment as to the conditions for evolution based on the statistical consequences of Mendelian heredity. The most general conclusion is that evolution depends on a certain balance among its factors. There must be a gene mutation, but an excessive rate gives an array of freaks, not evolution; there must be selection, but too severe a process destroys the field of variability, and thus the basis for further advance; prevalence of local inbreeding within a species has extremely important evolutionary consequences, but too close inbreeding leads merely to extinction. A certain amount of crossbreeding is favorable but not too much. In this dependence on balance the species is like a living organism. At all levels of organization life depends on the maintenance of a certain balance among its factors.
In Proceedings of the Sixth International Congress of Genetics: Ithaca, New York, 1932 (1932) Vol. 1, 365.
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In man, population structure reaches its greatest complexity. Mankind—the human species, Homo sapiens—is the most inclusive Mendelian population, one which inhabits nearly the whole globe.
In Radiation, Genes, and Man (1959), 102.
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See also:
  • 22 Jul - short biography, births, deaths and events on date of Mendel's birth.
  • The Monk in the Garden: The Lost and Found Genius of Gregor Mendel, the Father of Genetics, by Robin Marantz Henig. - book suggestion.
  • Booklist for Gregor Mendel.

Carl Sagan Thumbnail In science it often happens that scientists say, 'You know that's a really good argument; my position is mistaken,' and then they would actually change their minds and you never hear that old view from them again. They really do it. It doesn't happen as often as it should, because scientists are human and change is sometimes painful. But it happens every day. I cannot recall the last time something like that happened in politics or religion. (1987) -- Carl Sagan
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