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Gregor Mendel, the "father of genetics"

The history of genetics is generally held to have started with the work Austrian monk, Gregor 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, an 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-chromosome theory of heredity, which was widely accepted by 1925. Alongside experimental work, mathematicians developed the statistical framework of population genetics, bring 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 problem 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.

Pre-Mendelian ideas on heredity

Ancient theories

The most influential early theories of heredity were that of Hippocrates 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, determining the shape of the female's menstrual blood through an organism's early development. For both Hippocrates and Aristotle—and nearly all Western scholars through 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.^[1]

Plant systematics and hybridization

In the 18th century, with increased knowledge of plant and animal diversity and the accompanying increased focus on taxonomy, 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.^[2]

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 develop a theoretical foundation for their work or to integrate their knowledge with work in physiology and natural history.Cite error: A <ref> tag is missing the closing </ref> (see the help page).

1956 Jo Hin Tjio and Albert Levan established the correct chromosome number in humans to be 46

1958 The Meselson-Stahl experiment demonstrates that DNA is semiconservatively replicated

1961 The genetic code is arranged in triplets

1964 Howard Temin showed using RNA viruses that Crick's central dogma is not always true

1970 Restriction enzymes were discovered in studies of a bacterium, Haemophilus influenzae, enabling scientists to cut and paste DNA

The genomics era

See genomics, history of genomics

1972, Walter Fiers and his team at the Laboratory of Molecular Biology of the University of Ghent (Ghent, Belgium) were the first to determine the sequence of a gene: the gene for bacteriophage MS2 coat protein^[3].

1976, Walter Fiers and his team determine the complete nucleotide-sequence of bacteriophage MS2-RNA^[4]

1977 DNA is sequenced for the first time by Fred Sanger, Walter Gilbert, and Allan Maxam working independently. Sanger's lab sequence the entire genome of Bacteriophage Φ-X174^[5].

1983 Kary Banks Mullis discovers the polymerase chain reaction enabling the easy amplification of DNA

1989 The human gene that encodes the CFTR protein was sequenced by Francis Collins and Lap-Chee Tsui. Defects in this gene cause cystic fibrosis.

1995 The genome of Haemophilus influenzae is the first genome of a free living organism to be sequenced

1996 Saccharomyces cerevisiae is the first eukaryote genome sequence to be released

1998 The first genome sequence for a multicellular eukaryote, Caenorhabditis elegans, is released

2001 First draft sequences of the human genome are released simultaneously by the Human Genome Project and Celera Genomics.

2003 (14 April) Successful completion of Human Genome Project with 99% of the genome sequenced to a 99.99% accuracy [1]

External links

References

^ Mayr, The Growth of Biological Thought, pp 635-640
^ Mayr, The Growth of Biological Thought, pp 640-649
^ Min Jou W, Haegeman G, Ysebaert M, Fiers W., Nucleotide sequence of the gene coding for the bacteriophage MS2 coat protein, Nature. 1972 May 12;237(5350):82-8
^ Fiers W et al., Complete nucleotide-sequence of bacteriophage MS2-RNA - primary and secondary structure of replicase gene, Nature, 260, 500-507, 1976
^ Sanger F, Air GM, Barrell BG, Brown NL, Coulson AR, Fiddes CA, Hutchison CA, Slocombe PM, Smith M., Nucleotide sequence of bacteriophage phi X174 DNA, Nature. 1977 Feb 24;265(5596):687-95

[1] Mayr, The Growth of Biological Thought, pp 635-640

[2] Mayr, The Growth of Biological Thought, pp 640-649

[3] Min Jou W, Haegeman G, Ysebaert M, Fiers W., Nucleotide sequence of the gene coding for the bacteriophage MS2 coat protein, Nature. 1972 May 12;237(5350):82-8

[4] Fiers W et al., Complete nucleotide-sequence of bacteriophage MS2-RNA - primary and secondary structure of replicase gene, Nature, 260, 500-507, 1976

[5] Sanger F, Air GM, Barrell BG, Brown NL, Coulson AR, Fiddes CA, Hutchison CA, Slocombe PM, Smith M., Nucleotide sequence of bacteriophage phi X174 DNA, Nature. 1977 Feb 24;265(5596):687-95

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 The '''history of genetics''' is generally held to have started with the work [[Austria]]n [[monk]], [[Gregor Mendel]]; [[Experiments on Plant Hybridization|his work]] on pea plants, published in 1866, described what came to be known as [[Mendelian inheritance]].  In the centuries before&mdash;and for several decades after&mdash;Mendel's work, an 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&mdash;most notably the fruit fly ''[[Drosophila melanogaster]]''.  Led by [[Thomas Hunt Morgan]] and his fellow "drosophilists", geneticists developed the [[Mendelian-chromosome theory of heredity]], which was widely accepted by 1925.  Alongside experimental work, mathematicians developed the statistical framework of [[population genetics]], bring 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 problem 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.
+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 problem 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.
 == Pre-Mendelian ideas on heredity ==