A brief history of the discovery of DNA: our evolving understanding of inheritance.

Evolution is a scientific fact. - see Not Just a Theory

“Evolution is the process of change in all forms of life over generations, and evolutionary biology is the study of how and why evolution occurs. An organism inherits features (called traits) from its parents through genes. Changes (called mutations) in these genes can produce a new trait in the offspring of an organism. If a new trait makes these offspring better suited to their environment, they will be more successful at surviving and reproducing. This process is called natural selection, and it causes useful traits to become more common. Over many generations, a population can acquire so many new traits that it becomes a new species.” - wikipedia

Charles Darwin’s classic work, “Origin of the Species”, 1859, forms the basis of our modern understanding of species evolution. Fundamental to Darwin’s work is the mechanism of change, natural selection. While evolution is no longer seriously questioned the process by which it occurs, natural selection, continues to be questioned. Two of the best known alternative concepts for the mechanism of evolution, though both are now largely discredited, are the pre-Darwin Jean-Baptiste Lamarck’s “acquired characteristics” - Lamarckism and Ernst Haeckel’s recapitulation theory.

Eventually, “… the union of traditional Darwinian evolution with subsequent discoveries in classical and molecular genetics termed the modern evolutionary synthesis, supported natural selection as the single primary explanation for adaptive evolution.

Thrown into the mix are political and social ideologies that have often sought to impose theories and actions on forced interpretations of evolution and evolutionary mechanisms, often with disastrous and tragic consequences. Two of the most well known are Lysenkoism in the former Soviet Union and the Eugenics movement in Europe and the United States. Eugenics, largely discredited by the 1930’s, has given us various actions from the U.S. Immigration Restrictions of the 1920’s to Action T4 in Nazi Germany.

Of course the most recent manifestation in the United States has been the controversy over Intelligent Design(ID). This movement has deep roots in American culture and draws on hypotheses such as orthogenesis and Lamarckism.

While controversies between ideologies will continue, the actual science leading to, and refining, our modern understanding of adaptive evolution in general and DNA in particular looks back to a humble setting with the pea hybridizing experiments of Gregor Mendel.

Additional readings   √
More on Evolution and its mechanism(s)

Pre-Darwinian ideas : Richard Dawkins : Stephen Jay Gould : Different views on the mechanism of evolution

The Complete Work of Charles Darwin Online
The Race for DNA - http://osulibrary.orst.edu/specialcollections/coll/pauling/dna/index.html
Linnus Pauling
Noble Prize Lectures of Interest - pdf
Thomas Hunt Morgan, 1934 Medicine. Lecture, December 11, 1965, “The relation of genetics to physiology and medicine
Jacques Monod, 1965 Medicine. Lecture, December 11, 1965, “From Enzymatic Adaption to Allosteric Transitions
Marshall Nirenberg, 1968 Medicine. Lecture, December 12, 1968, “The Genetic Code
Women scientists behind the scenes
Dr. Esther M. Zimmer Lederberg, 1922 - 2006
“Stanley Falkow said of Esther Lederberg that “Experimentally and methodologically she was a genius in the lab.”[15] However, although Esther Lederberg was a pioneer research scientist, she faced significant challenges as a woman scientist in the 1950s and 1960s. These were exacerbated by her collaboration with then-husband Joshua Lederberg.”
Daisy Roulland-Dussoix??
Can you find information about this scientist?
Nettie Maria Stephens, 1861 – 1912
Martha Chase, 1927 – 2003
“DNA’s role in heredity was confirmed in 1953, when Alfred Hershey and Martha Chase in the Hershey-Chase experiment, showed that DNA is the genetic material of the T2 phage. This experiment provided the crucial evidence that it was DNA itself, (which was shown to enter the cell), and not a protein,(which remained outside the cell), that was the carrier of information.” - citizendium.org
Independent functions of viral protein and nucleic acid in growth of bacteriophage, September, 1952 [pdf]
from The Journal of General Physiology
Rosalind Franklin, 1920 - 1958
mmmm
Cambridge Physics - The Structure of DNA
DNA Interactive part of the Gene Almanac from the Dolan DNA Learning Center of Cold Spring Harbor Laboratory

 

The Path to DNA

For thousands of years people have understood that characteristics of parents, plants and animals, are transmitted to offspring. Artificial selection has been practiced for many centuries. The question has always been, “How does inheritance happen? see Heredity

His 1859 book “On the Origin of Species”, Charles Darwin established evolution by common descent, through the process he called natural selection, as the dominant scientific explanation of diversification in nature.

From Darwin to Watson and Crick and to our understanding of DNA an its place in our life is a journey with many interesting turns. Outline below are a few of the significant steps along this journey.

 

Gregor Mendel

Gregor Mendel - 1865, 1866

Identifies inheritance “factors” in pea plants.
At this time there is no clear understanding of precisely how these “factors” are transmitted from parent to offspring.

“Mendel’s results were largely rejected. Though they were not completely unknown to biologists of the time, they were not seen as being crucial. Even Mendel himself did not see their ultimate applicability, and thought they only applied to certain categories of species. In 1900, however, the work was “re-discovered” by three European scientists, Hugo de Vries, Carl Correns, and Erich von Tschermak.

Its most vigorous promoter in Europe was William Bateson, who coined the term “genetics”, “gene”, and “allele” to describe many of its tenets. The model of heredity was highly contested by other biologists because it implied that heredity was discontinuous, in opposition to the apparently continuous variation observable. Many biologists also dismissed the theory because they were not sure it would apply to all species, and there seemed to be very few true Mendelian characters in nature. However later work by biologists and statisticians such as R.A. Fisher showed that if multiple Mendelian factors were involved for individual traits, they could produce the diverse amount of results observed in nature. Thomas Hunt Morgan and his assistants would later integrate the theoretical model of Mendel with the chromosome theory of inheritance, in which the chromosomes of cells were thought to hold the actual hereditary particles, and create what is now known as classical genetics,” - modified from wikipedia

Mendels Laws of Inheritance Law of Segregation : Law of Independent Assortment

The English text of Mendel’s 1866 published paper [pdf]
from Electronic Scholarly Publishing, Foundations of Classical Genetics
see also The English text of Mendel’s 1865 presented paper
see also wikipedia

Gregor Mendel. Why is this important?
The importance of Gregor Mendel's work went unrecognized for almost 40 years. It is one of the essential pieces of the puzzle that made up the modern synthesis. The idea of genes provided the mechanism by which traits can be passed to offspring, necessary for a variety of traits, and pairing of traits, to be present in descendent organisms. It is, in part, this variety of traits that natural selection acts upon. It is difficult to overstate the importance of Mendel's work and the impact of Mendelian genetics on the modern understanding of heredity.

 

 
Ernst Haeckel

Ernst Haeckel - 1865

Promoted Charles Darwin’s work in Germany but did not support natural selection

“Haeckel promoted Charles Darwin’s work in Germany and developed the controversial recapitulation theory (“ontogeny recapitulates phylogeny”) claiming that an individual organism’s biological development, or ontogeny, parallels and summarizes its species’ entire evolutionary development, or phylogeny.

Haeckel was a zoologist, an accomplished artist and illustrator, and later a professor of comparative anatomy. Although Haeckel’s ideas are important to the history of evolutionary theory, and he was a competent invertebrate anatomist most famous for his work on radiolaria, many speculative concepts that he championed are now considered incorrect.

Haeckel did not support natural selection, rather believing in a Lamarckian inheritance of acquired characteristics (Lamarckism). “ - wikipedia

Ernst Haeckel. Why is this important?
The importance of Gregor Mendel's work went unrecognized for almost 40 years. It is one of the essential pieces of the puzzle that made up the modern synthesis. The idea of genes provided the mechanism by which traits can be passed to offspring, necessary for a variety of traits, and pairing of traits, to be present in descendent organisms. It is, in part, this variety of traits that natural selection acts upon. It is difficult to overstate the importance of Mendel's work and the impact of Mendelian genetics on the modern understanding of heredity.

 

 
Friedrich Miescher

Friedrich Miescher - 1871

Isolates “nuclein” (DNA) from infected wounds.

Miescher, a physiological chemist was interested in studying the chemistry of the nucleus. He focused his research on leucocytes which were known to be the one of the main components in pus and could be obtained from bandages at the nearby hospital.

To extract the nucleus from pus cells Miescher devised different salt solutions eventually producing one with sodium sulfate. The cells were filtered. Since centrifuges were not present at this time the cells were allowed to settle at the bottom of a beaker. He then tried to isolate the nuclei free of cytoplasm.

He subjected the purified nuclei to an alkaline extraction followed by acidification resulting in a precipitate being formed which Miescher called nuclein (now known as DNA). Miescher and his students researched much of the nucleic acid chemistry but their function remained unknown.

modified from wikipedia

 
Oscar Hertwig

Oscar Hertwig - 1876, 1916

Refutes Darwin’s, Theory of Chance”.

“Hertwig was a leader in the field of comparative and causal animal-developmental history. He also wrote a leading textbook. He discovered fertilization of sea urchins, he recognized the role of the cell nucleus during inheritance and chromosome reduction during meiosis: in 1876, he found that fertilization includes the penetration of a spermatozoon into an egg cell. While Oscar was well interested in developmental biology, he was opposed to chance as assumed in Charles Darwin´s theory. His most important theoretical book was: “Das Werden der Organismen, eine Widerlegung der Darwinschen Zufallslehre” (Jena, 1916) (translation: “The Origin of Organisms - a Refutation of Darwin’s Theory of Chance”).“ - wikipedia

 
Wilhelm Johannsen

Wilhelm Johannsen - 1910

“The terms phenotype and genotype were created by Wilhelm Johannsen and first used in his paper in 1903. In his 1905 book, “Elemente der exakten Erblichkeitslehre” (The Elements of Heredity) he introduced the term gene. This term was coined in opposition to the then common pangene that stemmed from Darwin’s theory of pangenesis. The book became one of the founding texts of genetics.“ - wikipedia

 
Thomas Hunt Morgan

Thomas Hunt Morgan - 1910 - 1930

“Morgan’s findings about genes and their location on chromosomes helped transform biology into an experimental science. These findings formed the heart of Morgan’s most important idea: the chromosomal theory of heredity. He proposed that each chromosome contains a collection of small units called genes (a term he adopted from the Danish physiologist Wilhelm Johannsen who had lectured at Columbia in 1909), with different genes having specific locations along specific chromosomes.” - modified from Thomas Hunt Morgan at Columbia University - Eric R. Kandel

Famous for his, and his graduate students, work on the fruitfly Drosophila melanogaster. “In 1933 Morgan was awarded the Nobel Prize in Physiology or Medicine; he had been nominated in 1919 and 1930 for the same work. As an acknowledgement of the group nature of his discovery he gave his prize money to Calvin Bridges’, Alfred Henry Sturtevant’s and his own children.” - wikipedia

Noble Biography
Noble Lecture , “The Relation of Genetics to Physiology and Medicine” [pdf], June 4, 1934

 
Phoebus Levene
Phoebus Levene - 1910

Describes building blocks of DNA, including four types of base,
AAdenine  : CCytosine  : TThymine  : GGuanine

“He also showed that the components were linked together in the order phosphate-sugar-base to form units. He called each of these units a nucleotide, and stated that the DNA molecule consisted of a string of nucleotide units linked together through the phosphate groups, which are the ‘backbone’ of the molecule. His ideas about the structure of DNA were wrong; he thought there were only four nucleotides per molecule. He even declared that it could not store the genetic code because it was chemically far too simple. However, his work was a key basis for the later work that determined the structure of DNA.”

modified from wikipedia

 
Frederick Griffith

Frederick Griffith - 1928

Demonstrates a “transforming factor” that can transmit the ability of bacteria to cause pneumonia in mice.

The famous experiment was done when Griffith was trying to make a vaccine to prevent pneumonia infections in the “Spanish flu” influenza pandemic after World War I, by using two strains of the Streptococcus pneumoniae bacterium. After isolating bacteria from the blood of mice, Griffith discovered that the previously avirulent R bacteria had acquired capsules and had thus become the virulent S strain.

It wasn’t until several years later that Griffith’s “transforming principle” was identified as DNA by Oswald Theodore Avery, along with coworkers Colin MacLeod and Maclyn McCarty, in 1944. - modified from wikipedia

Note: Although DNA had been identified in cells, before Griffith’s experiment it was not considered a strong candidate for carrying the genetic material due to its simple form. - modified from citizendium.org

Frederick Griffith
from cuil.com

 
Ronald A. Fisher
J. B. S. Haldane
Sewall Wright
Ronald A. Fisher, J. B. S. Haldane and Sewall Wright - 1918-1930’s

Mendelian inheritance can result in natural selection.

Introduced rigorous statistical and mathematical methods

Recognized as the founders of population genetics. Population genetics served as the stimulus for the development of modern evolutionary synthesis. Julian Huxley invented the term, when he produced his book, Evolution: The Modern Synthesis (1942). Other major figures in the modern synthesis include Theodosius Dobzhansky, E.B. Ford, Ernst Mayr, Bernhard Rensch, Sergei Chetverikov, George Gaylord Simpson, and G. Ledyard Stebbins.

modified from wikipedia

Ronald A. Fisher : J. B. S. Haldane : Sewall Wright

Fisher’s original paper. “The Correlation Between Relatives on the Supposition of Mendelian Inheritance” [pdf], 1918.
In this paper “Fisher puts forward a genetic model that shows that continuous variation amongst characters could be the result of Mendelian inheritance. The paper also contains the first use of the term variance.” - wikipedia

Haldane applied mathematical analysis to real world examples of natural selection. He established that natural selection could work in the real world at a faster rate than even Fisher had assumed. - wikipedia

“Sewall Wright focused on combinations of genes that interacted as complexes, and the effects of inbreeding on small relatively isolated populations, which could exhibit genetic drift. In a 1932 paper he introduced the concept of an adaptive landscape in which phenomena such as cross breeding and genetic drift in small populations could push them away from adaptive peaks, which would in turn allow natural selection to push them towards new adaptive peaks.” - wikipedia

 
Oswald Avery
Oswald Avery, Colin MacLeod and Maclyn McCarty - 1944

“In1943, Oswald Theodore Avery extended Griffith’s work and discovered that traits of the virulent form of Pneumococcus could be transferred to the avirulent form of the same bacteria by mixing killed virulent bacteria with the live avirulent form. Avery identified DNA as the transforming factor. This discovery is considered by some to be a major breakthrough enabling new research methods and a new focus on DNA itself and therefore represents the birth of molecular biology.“ - citizendium.org

Studies on the chemical nature of the substance inducing transformation of pneumococcal types[pdf]
With an informative introduction.
A reprint of their 1944 article from The Journal of Experimental Medicine
see also wikipedia Oswald Avery : Colin MacLeod : Maclyn McCarty

 
Erwin Chargaff

Erwin Chargaff - 1950

Discovered a one-to-one ratio of A:T and G:C in DNA samples from a variety of organisms.

“In 1950, Erwin Chargaff published a paper in which he described something he found extraordinary: the ratios of adenine to thymine were equal, as well as cytosine to guanine. He called this the complementary situation, but later it became known as the Chargaff Ratios. This discovery would play a crucial role in determining the structure of DNA.” - citizendium.org

wikipedia

 
Alfred D Hershey
Martha Chase

Alfred Hershey and Martha Chase - 1952

“DNA’s role in heredity was confirmed in 1953, when Alfred Hershey and Martha Chase in the Hershey-Chase experiment, showed that DNA is the genetic material of the T2 phage. This experiment provided the crucial evidence that it was DNA itself, (which was shown to enter the cell), and not a protein,(which remained outside the cell), that was the carrier of information.” - citizendium.org

see also wikipedia Alfred D. Hershey : Martha C. Chase

Alfred D. Hershey’s Noble Lecture [pdf], “Idiosyncrasies of DNA structure”, December 12, 1969

 
Rosalind Franklin

Rosalind Franklin - 1951

Created a high quality X-ray diffraction photograph to reveal more detail of the repeating structure of DNA.

“Franklin was an English biophysicist and X-ray crystallographer who made very important contributions to the understanding of the fine structures of DNA, viruses, coal and graphite. Franklin is best known for her work on the X-ray diffraction images of DNA which were an important influence on Crick and Watson’s 1953 hypothesis regarding the structure of DNA. When her work was published it also presented critical evidence in support of their hypothesis.

For a discussion of Franklin’s contribution to the model of DNA and the recognition of her contribution, see wikipedia

The Secret of Photo 51 from NOVA

 
James Watson
Francis Crick
Maurice Wilkins

James Watson, Francis Crick and Maurice Wilkins - 1952

Aided by access to Franklin’s data Watson and Crick refined their early triple spiral model and, like Franklin, suggested the double helix as the three-dimensional structure of the DNA molecule.

see also wikipedia James Watson : Francis Crick : Maurice Wilkins

James Watson’s Noble Lecture [pdf], “The Involvement of RNA in the Synthesis of Proteins”, December 11, 1962
Francis Crick’s Noble Lecture, “On the Genetic Code”, December 11, 1962
Maurice Wilkins’ Noble Lecture [pdf], “The molecular configuration of nucleic acids”, December 11, 1961

 

Other DNA Timelines

DNA > Draft and DNA Timelines from citizendium.org
A very clear sequencing and explanation of the road toward understanding DNA. Frequently cited in the outline above.
 
DNA timeline part of the Gene Almanac from the Dolan DNA Learning Center of Cold Spring Harbor Laboratory
A more detailed presentation of the individual researchers than we have presented in the above outline.
 
Key accomplishments: DNA part of the Visible Proofs: Forensic Views of the Body [a mystery]
sponsored by the The National Library of Medicine
 
Genetics in Context from Electronic Scholarly Publishing
Two parallel tracks of the developments in Genetics and world events.
Be sure to look through the list of publications in the Foundations of Classical Genetics in the Collection of Publications section.
 

Presentations concerning DNA

James Watson: The double helix and today's DNA mysteries a TED Talk
“Nobel laureate James Watson opens TED2005 with the frank and funny story of how he and his research partner, Francis Crick, discovered the structure of DNA.”
 
Paul Rothemund: Casting spells with DNA a TED Talk
“Paul Rothemund writes code that causes DNA to arrange itself into a star, a smiley face and more. Sure, it’s a stunt, but it’s also a demonstration of self-assembly at the smallest of scales — with vast implications for the future of making things.”
 
close

 

The Virtual Genome Project is funded by the National Science Foundation Microbial Genome Sequencing Program, Grant number: EF-0627988.
For more information contact: Dr. Eva Top, Professor of Biology, Department of Biological Sciences, University of Idaho, Moscow, I.D. 83844-3051 U.S.A.
email: etop [at] uidaho.edu

spacer image