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Classical Genetics: Foundations
- Mendel, Gregor. 1865.
Experiments in plant hybridization. Verhandlungen des naturforschenden
Vereines in Brünn, Bd. IV für das Jahr 1865, Abhandlungen, 3-47.
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In February and March of 1865, Gregor Mendel presented the Brünn Natural
History Society in Brünn, Czechoslovakia, with the results of his
investigations into the mechanisms governing inheritance in pea plants.
The next year, the work was published as Mendel, Gregor. 1866. "Versuche
über Pflanzen Hybriden." Verhandlungen des naturforschenden
Vereines in Brünn, 4:3-47.
In this remarkable paper, Mendel laid the groundwork for later became
the science of genetics. However, the work was largely ignored when it
appeared and Mendel moved on to other things. He died in 1884.
His work was rediscovered at the turn of the century and its significance
immediately recognized. Genetics, as a formal scientific discipline, exploded
into activity in 1900.
An annotated version
of Mendel's paper is also available. The annotated version contains explanatory
notes throughout the document. This can be useful to those reading Mendel's
paper for the first time.
For those wishing to see and read Mendel in the original, a
reprint edition is available. This version is in Adobe PDF format, but
the pages are images of the original publication, not a new tyoe-setting of
the material. This is a large file (2,142,414 bytes).
You may also with to visit The
Mendel Web site, maintained at NETSPACE.ORG by Roger Blumberg. A
MIRROR SITE of MendelWeb is maintained at the University of
Washington. The site offers many additional resources for the
- Bateson, William. 1899.
Hybridisation and cross-breeding as a method of scientific investigation.
Journal of the Royal Horticultural Society, 24:59-66.
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In this talk, given in 1899, before Mendel's work had been rediscovered,
Bateson gives his vision of what kind of research will be necessary to shed
light on the processes of inheritance and evolution:
What we first require is to know what happens when a variety is crossed with
its nearest allies. If the result is to have a scientific value, it is almost
absolutely necessary that the offspring of such crossing should then be examined
statistically. It must be recorded how many of the offspring resembled each
parent and how many shewed characters intermediate between those of the parents.
If the parents differ in several characters, the offspring must be examined
statistically, and marshalled, as it is called, in respect of each of those
One would be hard pressed to provide a better anticipation of the experimental
approach of Gregor Mendel. Small wonder that Bateson, upon encountering Mendel's
work, quickly became convinced that the correct method for studying inheritance
was finally at hand.
- Bateson, William. 1900.
Problems of heredity as a subject for horticultural investigation
Journal of the Royal Horticultural Society, 25:54-61.
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Mendel's work of 1865 was largely neglected, until 1900 when it
was simultaneously rediscovered by Hugo de Vries, Carl Correns, and
Erik von Tschermak. When Mendel's work came to the attention of
William Bateson (who himself had already been advocating controlled
crosses as an approach to studying heredity), he was convinced that
Mendel's work was of major importance:
That we are in the presence of a new principle of the highest
importance is, I think, manifest. To what further conclusions it may
lead us cannot yet be foretold.
Bateson devoted the remainder of his scientific career to further
elucidations of "Mendelism." This present paper captures the enthusiasm
of Bateson's first encounter with the works of Mendel.
- Garrod, Archibald E. 1902.
The incidence of alkaptonuria: A study in chemical individuality.
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This paper is a true classic. Like Mendel's own work, this report
offers insights so far ahead of its time that it, and Garrod's follow-on
work, were largely neglected, until later efforts to elucidate the
physiological functioning of genes led to the Nobel-prize-winning
one-gene, one-enzyme hypothesis.
Less than two years after the rediscovery of Mendelism and just a few
years after the word biochemistry was first coined, Garrod
reports on alkaptonuria in humans and comes to the conclusion that
it is inherited as a Mendelian recessive and that the occurrence of
mutations (sports in the word of the time) in metabolic function
should be no more surprising than inherited variations in morphology.
- Sutton, Walter S. 1902.
On the morphology of the chromosome group in Brachystola magna.
Biological Bulletin, 4:24-39.
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In this paper, Sutton reports cytological studies of grasshopper chromosomes
that lead him to conclude that (a) chromosomes have individuality, (b) that they
occur in pairs, with one member of each pair contributed by each parent, and
(c) that the paired chromosomes separate from each other during meiosis.
After presenting considerable evidence for his assertions, Sutton closes his
paper with a sly reference to its undoubted significance:
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. To this subject I hope soon to return
in another place.
- Hardy, G. H. 1908.
Mendelian Proportions in a Mixed Population.
Science, NS. XXVIII:49-50
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Every geneticist has heard of the Hardy-Weinberg Law and of
Hardy-Weinberg Equilibrium, and nearly all basic biology texts teach that G. H.
Hardy played a seminal role in founding population genetics.
But, what most biologists don't realize
is that Hardy's total contribution to biology consisted of a single
letter to the editor in Science.
The letter began,
I am reluctant to
intrude in a discussion concerning matters of which I have no expert
knowledge, and I should have expected the very simple point which I wish
to make to have been familiar to biologists. However, some remarks
of Mr. Udny Yule, to which Mr. R. C. Punnett has called my attention,
suggest that it may still be worth making.
With that, Hardy offered his "simple point" and then washed his hands of
biology. His autobiography, A Mathematician's Apology, makes no
mention of population genetics.
- Morgan, Thomas, H. 1909.
What are "factors" in Mendelian explanations? American Breeders Association
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Although T. H. Morgan is best known for heading the genetics laboratory
at Columbia University (later at Cal Tech) that essentially defined
American genetics research for decades, he was initially skeptical of the
facile manner in which combinations of alleged Mendelian factors were being
invoked to explain all manner of heritable traits.
This paper begins with a wonderful debunking of easy explanation:
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 invoked; if two prove insufficient, three will sometimes
work out. The superior jugglery sometimes necessary to account for the
result, may blind us, if taken too naïvely, 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.
- Bridges, Calvin B. 1914.
Direct proof through non-disjunction that the sex-linked genes of
Drosophila are borne on the X-chromosome.
Science, NS vol. XL:107-109
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Although Bridges' longer 1916 Genetics paper (vol 1, page 1) on the
same topic is better known and treats the issue at much greater length, this short
communication in Science contains the same argument and is equally
By 1910, much evidence had been presented to demonstrate that sexual phenotype
(i.e., maleness or femaleness) was determined by chromosomes. And, as early as
1902 Sutton noted
that similarities in the behavior of genes and chromosomes suggested that
Mendelian factors might be carried on chromosomes.
Here, Bridges shows that mis-assortment of the sex chromosomes is accompanied
by atypical inheritance patterns for sex-linked traits and he argues that
this proves that genes are carried on chromosomes. He concludes his
paper: "there can be no doubt that the complete parallelism
between the unique behavior of the chromosomes and the behavior of sex-linked
genes and sex in this case means that the sex-linked genes are located in and
borne by the X-chromosomes."
- Muller, Herbert J. 1922.
Variation due to change in the individual gene.
The American Naturalist, 56:32-50.
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This paper is from an address given by to the thirty-ninth annual
meeting of the American Society of Naturalists, held in Toronto on
29 December 29 1921.
In this remarkably prescient analysis, Muller lays out the paradoxical
nature of the genetic material. It is apparently both autocatalytic
(i.e., directs its own synthesis) and heterocatalytic
(i.e., directs the sythesis of other molecules), yet only
the heterocatalytic function seems subject to mutation. With this,
he defines the key problems that must be solved for a successful
chemical model of the gene.
Muller also anticipated the ultimate development of molecular genetics:
That two distinct kinds of substances -- the d'Hérelle substances
(NOTE: viruses) and the genes -- should both possess this most
remarkable property of heritable variation or "mutability," each
working by a totally different mechanism, is quite conceivable,
considering the complexity of protoplasm, yet it would seem a
curious coincidence indeed. It would open up the possibility of
two totally different kinds of life, working by different mechanisms.
On the other hand, if these d'Hérelle bodies were really genes,
fundamentally like our chromosome genes, they would give us an
utterly new angle from which to attack the gene problem. They are
filterable, to some extent isolable, can be handled in test tubes,
and their properties, as shown by their effects on the bacteria,
can then be studied after treatment. It would be very rash to call
these bodies genes, and yet at present we must confess that there
is no distinction known between the genes and them. Hence we
cannot categorically deny that perhaps we may be able to grind
genes in a mortar and cook them in a beaker after all. Must we
geneticists become bacteriologists, physiological chemists and
physicists, simultaneously with being zoologists and botanists?
Let us hope so.
- Riddle, Oscar. 1924.
Any Hereditary Character and the Kinds of Things We Need to Know
The American Naturalist, LVIII:410-425.
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This does not qualify as a classic genetics paper and I suspect
that it has never before been included in a collection of important papers.
However, it is included here because it provides a glimpse into some general
aspects of genetic thought in the mid 1920's.
The premise of this essay is essentially that, as of its writing, "
studies on heredity and evolution offer what is mainly a two-sided attack
on a many-sided problem." This argument was well taken, but the
modern reader may have difficulty appreciating other concerns of the essay.
- Wright, Sewall. 1932.
Complementary Factors for Eye Color in Drosophila
The American Naturalist, LXVI:282-283.
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There are two distinct biochemical pathways producing pigments that
color the eyes of Drosophila melanogaster -- one yields a bright
red pigment, the other brown. When both are present, the eyes are
dark-red. When one is present and the other absent, flies have brown or
bright red eyes. When both are missing, flies have white eyes.
In 1932, Sewall Wright reported the first case where a cross between
red-eyed and brown-eyed flies yielded double-recessive progeny with white
eyes. What makes this observation interesting is that the work occurred as
part of a class exercise in an undergraduate teaching laboratory at the
University of Chicago. Not many modern undergraduate lab exercises yield