History of genetics
Encyclopedia
The history of genetics
started with the work of the Augustinian friar Gregor Johann Mendel. His work
on pea plants, published in 1866, described what came to be known as Mendelian Inheritance
. In the centuries before—and for several decades after—Mendel's work, a wide variety of theories of heredity
proliferated.
1900 marked the "rediscovery of Mendel" by Hugo de Vries
, Carl Correns
and Erich von Tschermak
, and by 1915 the basic principles of Mendelian genetics had been applied to a wide variety of organisms—most notably the fruit fly Drosophila melanogaster
. Led by Thomas Hunt Morgan
and his fellow "drosophilists", geneticists developed the Mendelian, which was widely accepted by 1925. Alongside experimental work, mathematicians developed the statistical framework of population genetics
, bringing genetical explanations into the study of evolution
.
With the basic patterns of genetic inheritance established, many biologists turned to investigations of the physical nature of the gene
. In the 1940s and early 1950s, experiments pointed to DNA
as the portion of chromosomes (and perhaps other nucleoproteins) that held genes. A focus on new model organisms such as viruses and bacteria, along with the discovery of the double helical structure of DNA in 1953, marked the transition to the era of molecular genetics
.
In the following years, chemists developed techniques for sequencing both nucleic acids and proteins, while others worked out the relationship between the two forms of biological molecules: the genetic code
. The regulation of gene expression
became a central issue in the 1960s; by the 1970s gene expression could be controlled and manipulated through genetic engineering
. In the last decades of the 20th century, many biologists focused on large-scale genetics projects, sequencing entire genomes.
and Aristotle
. Hippocrates' theory (possibly based on the teachings of Anaxagoras
) was similar to Darwin's later ideas on pangenesis
, involving heredity material that collects from throughout the body. Aristotle suggested instead that the (nonphysical) form-giving principle
of an organism was transmitted through semen (which he considered to be a purified form of blood) and the mother's menstrual blood, which interacted in the womb to direct an organism's early development. For both Hippocrates and Aristotle—and nearly all Western scholars through to the late 19th century—the inheritance of acquired characters
was a supposedly well-established fact that any adequate theory of heredity had to explain. At the same time, individual species were taken to have a fixed essence
; such inherited changes were merely superficial.
In the 9th century CE, the Afro-Arab
writer Al-Jahiz
considered the effects of the environment
on the likelihood of an animal to survive.
In 1000 CE, the Arab physician, Abu al-Qasim al-Zahrawi (known as Albucasis in the West) was the first physician to describe clearly the hereditary nature of haemophilia
in his Al-Tasrif
.
, new ideas about heredity began to appear. Linnaeus and others (among them Joseph Gottlieb Kölreuter
, Carl Friedrich von Gärtner, and Charles Naudin) conducted extensive experiments with hybridization, especially species hybrids. Species hybridizers described a wide variety of inheritance phenomena, include hybrid sterility and the high variability of back-crosses.
Plant breeders were also developing an array of stable varieties in many important plant species. In the early 19th century, Augustin Sageret established the concept of dominance
, recognizing that when some plant varieties are crossed, certain characters (present in one parent) usually appear in the offspring; he also found that some ancestral characters found in neither parent may appear in offspring. However, plant breeders made little attempt to establish a theoretical foundation for their work or to share their knowledge with current work of physiology, although Gartons Agricultural Plant Breeders
in England explained their system in their butt-holes.
first traced inheritance patterns of certain traits in pea plants and showed that they obeyed simple statistical rules. Although not all features show these patterns of Mendelian inheritance
, his work acted as a proof that application of statistics to inheritance could be highly useful. Since that time many more complex forms of inheritance have been demonstrated.
From his statistical analysis Mendel defined a concept that he described as an allele
, which was the fundamental unit of heredity. The term allele as Mendel used it is nearly synonymous with the term gene, and now means a specific variant of a particular gene.
Mendel's work was published in 1866 as "Versuche über Pflanzen-Hybriden" (Experiments on Plant Hybridization
) in the Verhandlungen des Naturforschenden Vereins zu Brünn (Proceedings of the Natural History Society of Brünn), following two lectures he gave on the work in early 1865.
, and it was not given any attention in the scientific community. Instead, discussions about modes of heredity were galvanized by Darwin
's theory of evolution
by natural selection, in which mechanisms of non-Lamarckian heredity seemed to be required. Darwin's own theory of heredity, pangenesis
, did not meet with any large degree of acceptance. A more mathematical version of pangenesis, one which dropped much of Darwin's Lamarckian holdovers, was developed as the "biometrical" school of heredity by Darwin's cousin, Francis Galton
. Under Galton and his successor Karl Pearson
, the biometrical school attempted to build statistical models for heredity and evolution, with some limited but real success, though the exact methods of heredity were unknown and largely unquestioned.
, Carl Correns
and Erich von Tschermak
There was then a feud between Bateson
and Pearson
over the hereditary mechanism. Fisher
solved this in "The Correlation Between Relatives on the Supposition of Mendelian Inheritance
".
Genetics
Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....
started with the work of the Augustinian friar Gregor Johann Mendel. His work
Experiments on Plant Hybridization
Written in 1865 by Gregor Mendel, Experiments on Plant Hybridization was the result after years spent studying genetic traits in pea plants. Mendel read his paper to the Natural History Society of Brünn on February 8 and March 8, 1865...
on pea plants, published in 1866, described what came to be known as Mendelian Inheritance
Mendelian inheritance
Mendelian inheritance is a scientific description of how hereditary characteristics are passed from parent organisms to their offspring; it underlies much of genetics...
. In the centuries before—and for several decades after—Mendel's work, a wide variety of theories of heredity
Heredity
Heredity is the passing of traits to offspring . This is the process by which an offspring cell or organism acquires or becomes predisposed to the characteristics of its parent cell or organism. Through heredity, variations exhibited by individuals can accumulate and cause some species to evolve...
proliferated.
1900 marked the "rediscovery of Mendel" by Hugo de Vries
Hugo de Vries
Hugo Marie de Vries ForMemRS was a Dutch botanist and one of the first geneticists. He is known chiefly for suggesting the concept of genes, rediscovering the laws of heredity in the 1890s while unaware of Gregor Mendel's work, for introducing the term "mutation", and for developing a mutation...
, Carl Correns
Carl Correns
Carl Erich Correns was a German botanist and geneticist, who is notable primarily for his independent discovery of the principles of heredity, and for his rediscovery of Gregor Mendel's earlier paper on that subject, which he achieved simultaneously but independently of the botanists Erich...
and Erich von Tschermak
Erich von Tschermak
Erich von Tschermak-Seysenegg was an Austrian agronomist who developed several new disease-resistant crops, including wheat-rye and oat hybrids. He was a son of the Moravia-born mineralogist Gustav Tschermak von Seysenegg...
, and by 1915 the basic principles of Mendelian genetics had been applied to a wide variety of organisms—most notably the fruit fly Drosophila melanogaster
Drosophila melanogaster
Drosophila melanogaster is a species of Diptera, or the order of flies, in the family Drosophilidae. The species is known generally as the common fruit fly or vinegar fly. Starting from Charles W...
. Led by Thomas Hunt Morgan
Thomas Hunt Morgan
Thomas Hunt Morgan was an American evolutionary biologist, geneticist and embryologist and science author who won the Nobel Prize in Physiology or Medicine in 1933 for discoveries relating the role the chromosome plays in heredity.Morgan received his PhD from Johns Hopkins University in zoology...
and his fellow "drosophilists", geneticists developed the Mendelian, which was widely accepted by 1925. Alongside experimental work, mathematicians developed the statistical framework of population genetics
Population genetics
Population genetics is the study of allele frequency distribution and change under the influence of the four main evolutionary processes: natural selection, genetic drift, mutation and gene flow. It also takes into account the factors of recombination, population subdivision and population...
, bringing genetical explanations into the study of evolution
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
.
With the basic patterns of genetic inheritance established, many biologists turned to investigations of the physical nature of the gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
. In the 1940s and early 1950s, experiments pointed to DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
as the portion of chromosomes (and perhaps other nucleoproteins) that held genes. A focus on new model organisms such as viruses and bacteria, along with the discovery of the double helical structure of DNA in 1953, marked the transition to the era of molecular genetics
Molecular genetics
Molecular genetics is the field of biology and genetics that studies the structure and function of genes at a molecular level. The field studies how the genes are transferred from generation to generation. Molecular genetics employs the methods of genetics and molecular biology...
.
In the following years, chemists developed techniques for sequencing both nucleic acids and proteins, while others worked out the relationship between the two forms of biological molecules: the genetic code
Genetic code
The genetic code is the set of rules by which information encoded in genetic material is translated into proteins by living cells....
. The regulation of gene expression
Gene expression
Gene expression is the process by which information from a gene is used in the synthesis of a functional gene product. These products are often proteins, but in non-protein coding genes such as ribosomal RNA , transfer RNA or small nuclear RNA genes, the product is a functional RNA...
became a central issue in the 1960s; by the 1970s gene expression could be controlled and manipulated through genetic engineering
Genetic engineering
Genetic engineering, also called genetic modification, is the direct human manipulation of an organism's genome using modern DNA technology. It involves the introduction of foreign DNA or synthetic genes into the organism of interest...
. In the last decades of the 20th century, many biologists focused on large-scale genetics projects, sequencing entire genomes.
Ancient theories
The most influential early theories of heredity were that of HippocratesHippocrates
Hippocrates of Cos or Hippokrates of Kos was an ancient Greek physician of the Age of Pericles , and is considered one of the most outstanding figures in the history of medicine...
and Aristotle
Aristotle
Aristotle was a Greek philosopher and polymath, a student of Plato and teacher of Alexander the Great. His writings cover many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, linguistics, politics, government, ethics, biology, and zoology...
. Hippocrates' theory (possibly based on the teachings of Anaxagoras
Anaxagoras
Anaxagoras was a Pre-Socratic Greek philosopher. Born in Clazomenae in Asia Minor, Anaxagoras was the first philosopher to bring philosophy from Ionia to Athens. He attempted to give a scientific account of eclipses, meteors, rainbows, and the sun, which he described as a fiery mass larger than...
) was similar to Darwin's later ideas on pangenesis
Pangenesis
Pangenesis was Charles Darwin's hypothetical mechanism for heredity. He presented this 'provisional hypothesis' in his 1868 work The Variation of Animals and Plants under Domestication and felt that it brought 'together a multitude of facts which are at present left disconnected by any efficient...
, involving heredity material that collects from throughout the body. Aristotle suggested instead that the (nonphysical) form-giving principle
Theory of Forms
Plato's theory of Forms or theory of Ideas asserts that non-material abstract forms , and not the material world of change known to us through sensation, possess the highest and most fundamental kind of reality. When used in this sense, the word form is often capitalized...
of an organism was transmitted through semen (which he considered to be a purified form of blood) and the mother's menstrual blood, which interacted in the womb to direct an organism's early development. For both Hippocrates and Aristotle—and nearly all Western scholars through to the late 19th century—the inheritance of acquired characters
Inheritance of acquired characters
The inheritance of acquired characteristics is a hypothesis that physiological changes acquired over the life of an organism may be transmitted to offspring...
was a supposedly well-established fact that any adequate theory of heredity had to explain. At the same time, individual species were taken to have a fixed essence
Essentialism
In philosophy, essentialism is the view that, for any specific kind of entity, there is a set of characteristics or properties all of which any entity of that kind must possess. Therefore all things can be precisely defined or described...
; such inherited changes were merely superficial.
In the 9th century CE, the Afro-Arab
Afro-Arab
Afro-Arab refers to people of mixed Black African and genealogical Arab ancestral heritage and/or linguistically and culturally Arabized Black Africans...
writer Al-Jahiz
Al-Jahiz
Al-Jāḥiẓ was an Arabic prose writer and author of works of literature, Mu'tazili theology, and politico-religious polemics.In biology, Al-Jahiz introduced the concept of food chains and also proposed a scheme of animal evolution that entailed...
considered the effects of the environment
Natural environment
The natural environment encompasses all living and non-living things occurring naturally on Earth or some region thereof. It is an environment that encompasses the interaction of all living species....
on the likelihood of an animal to survive.
In 1000 CE, the Arab physician, Abu al-Qasim al-Zahrawi (known as Albucasis in the West) was the first physician to describe clearly the hereditary nature of haemophilia
Haemophilia
Haemophilia is a group of hereditary genetic disorders that impair the body's ability to control blood clotting or coagulation, which is used to stop bleeding when a blood vessel is broken. Haemophilia A is the most common form of the disorder, present in about 1 in 5,000–10,000 male births...
in his Al-Tasrif
Al-Tasrif
The Kitab al-Tasrif was an Arabic encyclopedia on medicine and surgery, written near the year 1000 by Abu al-Qasim al-Zahrawi...
.
Plant systematics and hybridization
In the 18th century, with increased knowledge of plant and animal diversity and the accompanying increased focus on taxonomyTaxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...
, new ideas about heredity began to appear. Linnaeus and others (among them Joseph Gottlieb Kölreuter
Joseph Gottlieb Kölreuter
Joseph Gottlieb Kölreuter , also spelled Koelreuter or Kohlreuter, was a German botanist.Kölreuter was born the son of a pharmacist in Karlsruhe, Germany, and grew up in Sulz. He studied medicine at the University of Tübingen under physician and botanist Johann Georg Gmelin, receiving his PhD in...
, Carl Friedrich von Gärtner, and Charles Naudin) conducted extensive experiments with hybridization, especially species hybrids. Species hybridizers described a wide variety of inheritance phenomena, include hybrid sterility and the high variability of back-crosses.
Plant breeders were also developing an array of stable varieties in many important plant species. In the early 19th century, Augustin Sageret established the concept of dominance
Dominance relationship
Dominance in genetics is a relationship between two variant forms of a single gene, in which one allele masks the effect of the other in influencing some trait. In the simplest case, if a gene exists in two allelic forms , three combinations of alleles are possible: AA, AB, and BB...
, recognizing that when some plant varieties are crossed, certain characters (present in one parent) usually appear in the offspring; he also found that some ancestral characters found in neither parent may appear in offspring. However, plant breeders made little attempt to establish a theoretical foundation for their work or to share their knowledge with current work of physiology, although Gartons Agricultural Plant Breeders
Gartons Agricultural Plant Breeders
This is a short history of the United Kingdom's first agricultural plant breeding business.Dr John Garton, of the firm of Garton Brothers of Newton-le-Willows in the United Kingdom was the Originator of Scientific Farm Plant Breeding. He is credited as the first scientist to show that the common...
in England explained their system in their butt-holes.
Mendel
In breeding experiments between 1856 and 1865, Gregor MendelGregor Mendel
Gregor Johann Mendel was an Austrian scientist and Augustinian friar who gained posthumous fame as the founder of the new science of genetics. Mendel demonstrated that the inheritance of certain traits in pea plants follows particular patterns, now referred to as the laws of Mendelian inheritance...
first traced inheritance patterns of certain traits in pea plants and showed that they obeyed simple statistical rules. Although not all features show these patterns of Mendelian inheritance
Mendelian inheritance
Mendelian inheritance is a scientific description of how hereditary characteristics are passed from parent organisms to their offspring; it underlies much of genetics...
, his work acted as a proof that application of statistics to inheritance could be highly useful. Since that time many more complex forms of inheritance have been demonstrated.
From his statistical analysis Mendel defined a concept that he described as an allele
Allele
An allele is one of two or more forms of a gene or a genetic locus . "Allel" is an abbreviation of allelomorph. Sometimes, different alleles can result in different observable phenotypic traits, such as different pigmentation...
, which was the fundamental unit of heredity. The term allele as Mendel used it is nearly synonymous with the term gene, and now means a specific variant of a particular gene.
Mendel's work was published in 1866 as "Versuche über Pflanzen-Hybriden" (Experiments on Plant Hybridization
Experiments on Plant Hybridization
Written in 1865 by Gregor Mendel, Experiments on Plant Hybridization was the result after years spent studying genetic traits in pea plants. Mendel read his paper to the Natural History Society of Brünn on February 8 and March 8, 1865...
) in the Verhandlungen des Naturforschenden Vereins zu Brünn (Proceedings of the Natural History Society of Brünn), following two lectures he gave on the work in early 1865.
Post-Mendel, pre-re-discovery
Mendel's work was published in a relatively obscure scientific journalScientific journal
In academic publishing, a scientific journal is a periodical publication intended to further the progress of science, usually by reporting new research. There are thousands of scientific journals in publication, and many more have been published at various points in the past...
, and it was not given any attention in the scientific community. Instead, discussions about modes of heredity were galvanized by Darwin
Charles Darwin
Charles Robert Darwin FRS was an English naturalist. He established that all species of life have descended over time from common ancestry, and proposed the scientific theory that this branching pattern of evolution resulted from a process that he called natural selection.He published his theory...
's theory of evolution
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
by natural selection, in which mechanisms of non-Lamarckian heredity seemed to be required. Darwin's own theory of heredity, pangenesis
Pangenesis
Pangenesis was Charles Darwin's hypothetical mechanism for heredity. He presented this 'provisional hypothesis' in his 1868 work The Variation of Animals and Plants under Domestication and felt that it brought 'together a multitude of facts which are at present left disconnected by any efficient...
, did not meet with any large degree of acceptance. A more mathematical version of pangenesis, one which dropped much of Darwin's Lamarckian holdovers, was developed as the "biometrical" school of heredity by Darwin's cousin, Francis Galton
Francis Galton
Sir Francis Galton /ˈfrɑːnsɪs ˈgɔːltn̩/ FRS , cousin of Douglas Strutt Galton, half-cousin of Charles Darwin, was an English Victorian polymath: anthropologist, eugenicist, tropical explorer, geographer, inventor, meteorologist, proto-geneticist, psychometrician, and statistician...
. Under Galton and his successor Karl Pearson
Karl Pearson
Karl Pearson FRS was an influential English mathematician who has been credited for establishing the disciplineof mathematical statistics....
, the biometrical school attempted to build statistical models for heredity and evolution, with some limited but real success, though the exact methods of heredity were unknown and largely unquestioned.
Classical genetics
The significance of Mendel's work was not understood until early in the twentieth century, after his death, when his research was re-discovered by other scientists working on similar problems. Hugo de VriesHugo de Vries
Hugo Marie de Vries ForMemRS was a Dutch botanist and one of the first geneticists. He is known chiefly for suggesting the concept of genes, rediscovering the laws of heredity in the 1890s while unaware of Gregor Mendel's work, for introducing the term "mutation", and for developing a mutation...
, Carl Correns
Carl Correns
Carl Erich Correns was a German botanist and geneticist, who is notable primarily for his independent discovery of the principles of heredity, and for his rediscovery of Gregor Mendel's earlier paper on that subject, which he achieved simultaneously but independently of the botanists Erich...
and Erich von Tschermak
Erich von Tschermak
Erich von Tschermak-Seysenegg was an Austrian agronomist who developed several new disease-resistant crops, including wheat-rye and oat hybrids. He was a son of the Moravia-born mineralogist Gustav Tschermak von Seysenegg...
There was then a feud between Bateson
William Bateson
William Bateson was an English geneticist and a Fellow of St. John's College, Cambridge...
and Pearson
Karl Pearson
Karl Pearson FRS was an influential English mathematician who has been credited for establishing the disciplineof mathematical statistics....
over the hereditary mechanism. Fisher
Ronald Fisher
Sir Ronald Aylmer Fisher FRS was an English statistician, evolutionary biologist, eugenicist and geneticist. Among other things, Fisher is well known for his contributions to statistics by creating Fisher's exact test and Fisher's equation...
solved this in "The Correlation Between Relatives on the Supposition of Mendelian Inheritance
The Correlation Between Relatives on the Supposition of Mendelian Inheritance
The Correlation Between Relatives on the Supposition of Mendelian Inheritance is a scientific paper by R.A. Fisher which was published in the Philosophical Transactions of the Royal Society of Edinburgh in 1918,...
".
- 1865: Gregor MendelGregor MendelGregor Johann Mendel was an Austrian scientist and Augustinian friar who gained posthumous fame as the founder of the new science of genetics. Mendel demonstrated that the inheritance of certain traits in pea plants follows particular patterns, now referred to as the laws of Mendelian inheritance...
's paper, Experiments on Plant HybridizationExperiments on Plant HybridizationWritten in 1865 by Gregor Mendel, Experiments on Plant Hybridization was the result after years spent studying genetic traits in pea plants. Mendel read his paper to the Natural History Society of Brünn on February 8 and March 8, 1865... - 1869: Friedrich MiescherFriedrich MiescherJohannes Friedrich Miescher was a Swiss physician and biologist. He was the first researcher to isolate and identify nucleic acid.-Biography:...
discovers a weak acid in the nuclei of white blood cells that today we call DNADNADeoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in... - 1880 - 1890: Walther FlemmingWalther FlemmingWalther Flemming was a German biologist and a founder of cytogenetics.He was born in Sachsenberg near Schwerin as the fifth child and only son of the psychiatrist Carl Friedrich Flemming and his second wife, Auguste Winter...
, Eduard StrasburgerEduard StrasburgerEduard Adolf Strasburger was a German professor who was one of the most famous botanists of the 19th century....
, and Edouard van BenedenEdouard Van BenedenEdouard Joseph Marie Van Beneden , son of Pierre-Joseph Van Beneden, was a Belgian embryologist, cytologist and marine biologist. He was professor of zoology at the University of Liège. He contributed to cytogenetics by his works on the roundworm Ascaris...
elucidate chromosome distribution during cell divisionCell divisionCell division is the process by which a parent cell divides into two or more daughter cells . Cell division is usually a small segment of a larger cell cycle. This type of cell division in eukaryotes is known as mitosis, and leaves the daughter cell capable of dividing again. The corresponding sort... - 1889: Hugo de VriesHugo de VriesHugo Marie de Vries ForMemRS was a Dutch botanist and one of the first geneticists. He is known chiefly for suggesting the concept of genes, rediscovering the laws of heredity in the 1890s while unaware of Gregor Mendel's work, for introducing the term "mutation", and for developing a mutation...
postulates that "inheritance of specific traits in organisms comes in particles", naming such particles "(pan)genes" - 1903: Walter SuttonWalter SuttonWalter Stanborough Sutton was an American geneticist and physician whose most significant contribution to present-day biology was his theory that the Mendelian laws of inheritance could be applied to chromosomes at the cellular level of living organisms...
hypothesizes that chromosomes, which segregate in a Mendelian fashion, are hereditary units - 1905: William BatesonWilliam BatesonWilliam Bateson was an English geneticist and a Fellow of St. John's College, Cambridge...
coins the term "genetics" in a letter to Adam SedgwickAdam SedgwickAdam Sedgwick was one of the founders of modern geology. He proposed the Devonian period of the geological timescale...
and at a meeting in 1906 - 1908: Hardy-Weinberg law derived.
- 1910: Thomas Hunt MorganThomas Hunt MorganThomas Hunt Morgan was an American evolutionary biologist, geneticist and embryologist and science author who won the Nobel Prize in Physiology or Medicine in 1933 for discoveries relating the role the chromosome plays in heredity.Morgan received his PhD from Johns Hopkins University in zoology...
shows that genes reside on chromosomes - 1913: Alfred SturtevantAlfred SturtevantAlfred Henry Sturtevant was an American geneticist. Sturtevant constructed the first genetic map of a chromosome in 1913. Throughout his career he worked on the organism Drosophila melanogaster with Thomas Hunt Morgan...
makes the first genetic map of a chromosome - 1913: Gene mapGene mapA gene map is the descriptive representation of the structure of a single gene. It includes the DNA sequence of a gene with introns and exons, 3' or 5' transcribed-untranslated regions, termination signal, regulatory elements such as promoters, enhancers and it may include known mutations defining...
s show chromosomes containing linear arranged genes - 1918: Ronald FisherRonald FisherSir Ronald Aylmer Fisher FRS was an English statistician, evolutionary biologist, eugenicist and geneticist. Among other things, Fisher is well known for his contributions to statistics by creating Fisher's exact test and Fisher's equation...
publishes "The Correlation Between Relatives on the Supposition of Mendelian InheritanceThe Correlation Between Relatives on the Supposition of Mendelian InheritanceThe Correlation Between Relatives on the Supposition of Mendelian Inheritance is a scientific paper by R.A. Fisher which was published in the Philosophical Transactions of the Royal Society of Edinburgh in 1918,...
" the modern synthesis of genetics and evolutionary biology starts. See population geneticsPopulation geneticsPopulation genetics is the study of allele frequency distribution and change under the influence of the four main evolutionary processes: natural selection, genetic drift, mutation and gene flow. It also takes into account the factors of recombination, population subdivision and population...
. - 1928: Frederick GriffithFrederick GriffithFrederick Griffith was a British bacteriologist whose focus was the epidemiology and pathology of bacterial pneumonia. In January 1928 he reported what is now known as Griffith's Experiment, the first widely accepted demonstrations of bacterial transformation, whereby a bacterium distinctly...
discovers that hereditary material from dead bacteriaBacteriaBacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
can be incorporated into live bacteria (see Griffith's experimentGriffith's experimentGriffith's experiment, reported in 1928 by Frederick Griffith, was one of the first experiments suggesting that bacteria are capable of transferring genetic information through a process known as transformation....
) - 1931: Crossing overChromosomal crossoverChromosomal crossover is an exchange of genetic material between homologous chromosomes. It is one of the final phases of genetic recombination, which occurs during prophase I of meiosis in a process called synapsis. Synapsis begins before the synaptonemal complex develops, and is not completed...
is identified as the cause of recombinationGenetic recombinationGenetic recombination is a process by which a molecule of nucleic acid is broken and then joined to a different one. Recombination can occur between similar molecules of DNA, as in homologous recombination, or dissimilar molecules, as in non-homologous end joining. Recombination is a common method... - 1933: Jean BrachetJean BrachetJean Louis Auguste Brachet was a Belgian biochemist who made a key contribution in understanding the role of RNA....
is able to show that DNADNADeoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
is found in chromosomes and that RNARNARibonucleic acid , or RNA, is one of the three major macromolecules that are essential for all known forms of life....
is present in the cytoplasmCytoplasmThe cytoplasm is a small gel-like substance residing between the cell membrane holding all the cell's internal sub-structures , except for the nucleus. All the contents of the cells of prokaryote organisms are contained within the cytoplasm...
of all cells. - 1941: Edward Lawrie TatumEdward Lawrie TatumEdward Lawrie Tatum was an American geneticist. He shared half of the Nobel Prize in Physiology or Medicine in 1958 with George Wells Beadle for showing that genes control individual steps in metabolism...
and George Wells Beadle show that genes code for proteinProteinProteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
s; see the original central dogma of genetics
The DNA era
- 1944: The Avery–MacLeod–McCarty experiment isolates DNADNADeoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
as the genetic material (at that time called transforming principle) - 1948: Barbara McClintockBarbara McClintockBarbara McClintock , the 1983 Nobel Laureate in Physiology or Medicine, was an American scientist and one of the world's most distinguished cytogeneticists. McClintock received her PhD in botany from Cornell University in 1927, where she was a leader in the development of maize cytogenetics...
discovers transposonTransposonTransposable elements are sequences of DNA that can move or transpose themselves to new positions within the genome of a single cell. The mechanism of transposition can be either "copy and paste" or "cut and paste". Transposition can create phenotypically significant mutations and alter the cell's...
s in maizeMaizeMaize known in many English-speaking countries as corn or mielie/mealie, is a grain domesticated by indigenous peoples in Mesoamerica in prehistoric times. The leafy stalk produces ears which contain seeds called kernels. Though technically a grain, maize kernels are used in cooking as a vegetable... - 1950: Erwin ChargaffErwin ChargaffErwin Chargaff was an American biochemist who emigrated to the United States during the Nazi era. Through careful experimentation, Chargaff discovered two rules that helped lead to the discovery of the double helix structure of DNA...
shows that the four nucleotides are not present in nucleic acids in stable proportions, but that some general rules appear to hold (e.g., that the amount of adenineAdenineAdenine is a nucleobase with a variety of roles in biochemistry including cellular respiration, in the form of both the energy-rich adenosine triphosphate and the cofactors nicotinamide adenine dinucleotide and flavin adenine dinucleotide , and protein synthesis, as a chemical component of DNA...
, A, tends to be equal to that of thymineThymineThymine is one of the four nucleobases in the nucleic acid of DNA that are represented by the letters G–C–A–T. The others are adenine, guanine, and cytosine. Thymine is also known as 5-methyluracil, a pyrimidine nucleobase. As the name suggests, thymine may be derived by methylation of uracil at...
, T). - 1952: The Hershey-Chase experimentHershey-Chase experimentThe Hershey–Chase experiments were a series of experiments conducted in 1952 by Alfred Hershey and Martha Chase, which helped to confirm that DNA was the genetic material. While DNA had been known to biologists since 1869, a few scientists still assumed at the time that proteins carried the...
proves the genetic information of phagesBacteriophageA bacteriophage is any one of a number of viruses that infect bacteria. They do this by injecting genetic material, which they carry enclosed in an outer protein capsid...
(and all other organisms) to be DNA - 1953: DNA structure is resolved to be a double helixHelixA helix is a type of smooth space curve, i.e. a curve in three-dimensional space. It has the property that the tangent line at any point makes a constant angle with a fixed line called the axis. Examples of helixes are coil springs and the handrails of spiral staircases. A "filled-in" helix – for...
by James D. WatsonJames D. WatsonJames Dewey Watson is an American molecular biologist, geneticist, and zoologist, best known as one of the co-discoverers of the structure of DNA in 1953 with Francis Crick...
and Francis CrickFrancis CrickFrancis Harry Compton Crick OM FRS was an English molecular biologist, biophysicist, and neuroscientist, and most noted for being one of two co-discoverers of the structure of the DNA molecule in 1953, together with James D. Watson... - 1956: Joe Hin TjioJoe Hin TjioJoe Hin Tjio , was a cytogeneticist renowned as the first person to recognize the normal number of human chromosomes. This epochal event occurred on December 22, 1955 at the Institute of Genetics of the University of Lund in Sweden, where Tjio was a visiting scientist.-Early life:Tjio was born to...
and Albert LevanAlbert LevanAlbert Levan was a Swedish botanist and geneticist.Albert Levan is best known today for co-authoring the report in 1956 that humans had forty-six chromosomes...
established the correct chromosomeChromosomeA chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...
number in humans to be 46 - 1958: The Meselson-Stahl experimentMeselson-Stahl experimentThe Meselson–Stahl experiment was an experiment by Matthew Meselson and Franklin Stahl in 1958 which supported the hypothesis that DNA replication was semiconservative. Semiconservative replication means that when the double stranded DNA helix was replicated, each of the two double stranded DNA...
demonstrates that DNA is semiconservatively replicatedSemiconservative replicationSemiconservative replication describes the mechanism by which DNA is replicated in all known cells.This mechanism of replication was one of three models originally proposedfor DNA replication:... - 1961 - 1967: Combined efforts of scientists "crack" the genetic codeGenetic codeThe genetic code is the set of rules by which information encoded in genetic material is translated into proteins by living cells....
, including Marshall Nirenberg, Har Gobind Khorana, Sydney BrennerSydney BrennerSydney Brenner, CH FRS is a South African biologist and a 2002 Nobel prize in Physiology or Medicine laureate, shared with H...
& Francis CrickFrancis CrickFrancis Harry Compton Crick OM FRS was an English molecular biologist, biophysicist, and neuroscientist, and most noted for being one of two co-discoverers of the structure of the DNA molecule in 1953, together with James D. Watson... - 1964: Howard Temin showed using RNA virusRNA virusAn RNA virus is a virus that has RNA as its genetic material. This nucleic acid is usually single-stranded RNA but may be double-stranded RNA...
es that the direction of DNA to RNA transcription can be reversed - 1970: Restriction enzymeRestriction enzymeA Restriction Enzyme is an enzyme that cuts double-stranded DNA at specific recognition nucleotide sequences known as restriction sites. Such enzymes, found in bacteria and archaea, are thought to have evolved to provide a defense mechanism against invading viruses...
s were discovered in studies of a bacterium, Haemophilus influenzaeHaemophilus influenzaeHaemophilus influenzae, formerly called Pfeiffer's bacillus or Bacillus influenzae, Gram-negative, rod-shaped bacterium first described in 1892 by Richard Pfeiffer during an influenza pandemic. A member of the Pasteurellaceae family, it is generally aerobic, but can grow as a facultative anaerobe. H...
, enabling scientists to cut and paste DNA
The genomics era
- 1972: Walter FiersWalter FiersWalter Fiers is a Belgian molecular biologist.He obtained a degree of Engineer for Chemistry and Agricultural Industries at the University of Ghent in 1954, and started his research career as an enzymologist in the laboratory of Laurent Vandendriessche in Ghent. In 1956-57, he worked with Heinz...
and his team at the Laboratory of Molecular Biology of the University of Ghent (GhentGhentGhent is a city and a municipality located in the Flemish region of Belgium. It is the capital and biggest city of the East Flanders province. The city started as a settlement at the confluence of the Rivers Scheldt and Lys and in the Middle Ages became one of the largest and richest cities of...
, BelgiumBelgiumBelgium , officially the Kingdom of Belgium, is a federal state in Western Europe. It is a founding member of the European Union and hosts the EU's headquarters, and those of several other major international organisations such as NATO.Belgium is also a member of, or affiliated to, many...
) were the first to determine the sequence of a gene: the gene for bacteriophage MS2Bacteriophage MS2The bacteriophage MS2 is an icosahedral, positive-sense single-stranded RNA virus that infects the bacterium Escherichia coli.-History:...
coat protein. - 1976: Walter Fiers and his team determine the complete nucleotide-sequence of bacteriophage MS2-RNA
- 1977: DNA is sequencedSequencingIn genetics and biochemistry, sequencing means to determine the primary structure of an unbranched biopolymer...
for the first time by Fred Sanger, Walter GilbertWalter GilbertWalter Gilbert is an American physicist, biochemist, molecular biology pioneer, and Nobel laureate.-Biography:Gilbert was born in Boston, Massachusetts, on March 21, 1932...
, and Allan MaxamAllan MaxamAllan Maxam is one of the pioneers of molecular genetics. He was one of the contributors to develop a DNA sequencing method at Harvard University, while working as a student in the laboratory of Walter Gilbert....
working independently. Sanger's lab sequence the entire genomeGenomeIn modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....
of bacteriophage Φ-X174. - 1983: Kary Banks Mullis discovers the polymerase chain reactionPolymerase chain reactionThe polymerase chain reaction is a scientific technique in molecular biology to amplify a single or a few copies of a piece of DNA across several orders of magnitude, generating thousands to millions of copies of a particular DNA sequence....
enabling the easy amplification of DNA - 1989: The humanHumanHumans are the only living species in the Homo genus...
gene that encodes the CFTRCystic fibrosis transmembrane conductance regulatorCystic fibrosis transmembrane conductance regulator is a protein that in humans is encoded by the CFTR gene.CFTR is a ABC transporter-class ion channel that transports chloride and thiocyanate ions across epithelial cell membranes...
protein was sequenced by Francis CollinsFrancis Collins (geneticist)Francis Sellers Collins , is an American physician-geneticist, noted for his discoveries of disease genes and his leadership of the Human Genome Project . He currently serves as Director of the National Institutes of Health in Bethesda, Maryland. Prior to being appointed Director, he founded and...
and Lap-Chee TsuiLap-Chee TsuiProfessor Lap-chee Tsui, OC, O.Ont is a Chinese-Canadian geneticist and currently the Vice-Chancellor and President of the University of Hong Kong.-Personal life:Tsui was born in Shanghai...
. Defects in this gene cause cystic fibrosisCystic fibrosisCystic fibrosis is a recessive genetic disease affecting most critically the lungs, and also the pancreas, liver, and intestine...
. - 1995: The genome of Haemophilus influenzae is the first genome of a free living organism to be sequenced
- 1996: Saccharomyces cerevisiaeSaccharomyces cerevisiaeSaccharomyces cerevisiae is a species of yeast. It is perhaps the most useful yeast, having been instrumental to baking and brewing since ancient times. It is believed that it was originally isolated from the skin of grapes...
is the first eukaryoteEukaryoteA eukaryote is an organism whose cells contain complex structures enclosed within membranes. Eukaryotes may more formally be referred to as the taxon Eukarya or Eukaryota. The defining membrane-bound structure that sets eukaryotic cells apart from prokaryotic cells is the nucleus, or nuclear...
genome sequence to be released - 1998: The first genome sequence for a multicellular eukaryote, Caenorhabditis elegansCaenorhabditis elegansCaenorhabditis elegans is a free-living, transparent nematode , about 1 mm in length, which lives in temperate soil environments. Research into the molecular and developmental biology of C. elegans was begun in 1974 by Sydney Brenner and it has since been used extensively as a model...
, is released - 2001: First draft sequences of the human genome are released simultaneously by the Human Genome ProjectHuman Genome ProjectThe Human Genome Project is an international scientific research project with a primary goal of determining the sequence of chemical base pairs which make up DNA, and of identifying and mapping the approximately 20,000–25,000 genes of the human genome from both a physical and functional...
and Celera GenomicsCelera GenomicsCelera Corporation was a business unit of the Applera Corporation, but was spun off in July 2008 to become an independent publicly traded company. In May 2011 Quest Diagnostics Incorporated completed the acquisition of Celera, which thus became a wholly owned subsidiary...
. - 2003 (14 April): Successful completion of Human Genome Project with 99% of the genome sequenced to a 99.99% accuracy http://www.genoscope.cns.fr/externe/English/Actualites/Presse/HGP/HGP_press_release-140403.pdf
See also
- List of sequenced eukaryotic genomes
- History of molecular biologyHistory of molecular biologyThe history of molecular biology begins in the 1930s with the convergence of various, previously distinct biological disciplines: biochemistry, genetics, microbiology, and virology...
- History of RNA BiologyHistory of RNA biologyNumerous key discoveries in biology have emerged from studies of RNA , including seminal work in the fields of biochemistry, genetics, microbiology, molecular biology, molecular evolution and structural biology. As of 2010, 30 scientists have been awarded Nobel Prizes for experimental work that...
External links
- Olby's "Mendel, Mendelism, and Genetics," at MendelWeb
- http://www.accessexcellence.org/AE/AEPC/WWC/1994/geneticstln.html
- http://www.sysbioeng.com/index/cta94-11s.jpg
- http://www.esp.org/books/sturt/history/
- http://cogweb.ucla.edu/ep/DNA_history.html
- http://news.bbc.co.uk/1/hi/in_depth/sci_tech/2000/human_genome/749026.stm