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Darwin's Theory of Evolution
On the Origin of Species, published on 24 November 1859, is a work of scientific literature by Charles Darwin which is considered to be the foundation of evolutionary biology. Darwin's Theory of Evolution states that "all species of organisms arise and develop through the natural selection of small, inherited variations that increase the individual's ability to compete, survive, and reproduce." -
Rediscovery of Mendel's Work
In the year 1900 Mendel's work was rediscovered by three botanists who then helped expand awareness of his laws of inheritance in the scientific world. Mendel is credited as being the founder of the modern science of genetics. One of his most famous findings was his principles of inheritance containing three laws: Law of Segregation, Law of Independent Assortment, and Fundamental Theory of Heredity. -
The Word Gene Coined
Danish botanist Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity. He also made the distinction between the outward appearance of an individual (phenotype) and its genetic traits (genotype). The proposed word traced from the Greek word genos, meaning "birth". The word spawned others, like genome. -
X-ray Diffraction of DNA
William Astbury, a British scientist, obtained the first X-ray diffraction pattern of DNA. X-ray diffraction patterns of crystallized molecules can reveal their structures with atomic precision. He extracted DNA from cells, then dipped a needle into the viscous DNA solution and dragged out a strand containing many molecules lined up roughly parallel to each other. The X-ray diffraction patterns off this strand revealed that DNA must have a regular, periodic structure. H -
46 Human Chromosomes
In 1995 Joe Hin Tjio defined 46 as the exact number of human chromosomes. Since then, technical advances in the field of cytogenetics - the study of chromosomes visually - have made the identification of chromosomes and of abnormalities like deletions and translocations more clear-cut. 1950's:
1952: Genes are Made of DNA
1953: DNA Double Helix
1955: DNA Copying Enzyme
1956: Cause of Disease Traced to Alteration
1958: Semiconservative Replication of DNA
1959: Chromosome Abnormalities Identified -
Genetic Code Cracked
In 1966, Marshall Nirenberg, Har Khorana and Severo Ochoa and colleagues explained the genetic code showing how nucleic acids with their 4-letter alphabet determine the order of the 20 kinds of amino acids in proteins. Messenger RNA is interpreted three letters at a time; a set of three nucleotides forms a "codon" that encodes an amino acid. A three-letter word made of four possible letters can have 64 permutations, which is more than enough to encode the 20 amino acids in living beings. -
First Animal Gene Cloned
Stanford and UCSF researchers fused a segment of DNA containing a gene from the African clawed frog Xenopus with DNA from the bacterium E. coli and placed the resulting DNA back into an E. coli cell. There, the frog DNA was copied and the gene it contained directed the production of a specific frog protein. This was the first time an animal gene was cloned. -
First Transgenic Mice and Fruit Flies
Scientists had been able to add new genes to bacterial cells for several years. In the early 1980s, they figured out how to add stably-inherited new genes to animals. The first such "transgenic animals" were mice and fruit flies. By adding foreign genes or genes spelled slightly differently than normal, scientists had a new way to test the functions of genes. -
Launch of the Human Genome Project
The Human Genome Project (HGP) is an international scientific research project with the goal of determining the sequence of chemical base pairs which make up human DNA, and of identifying and mapping all of the genes of the human genome from both a physical and a functional standpoint. The Human Genome Project officially began in 1990. -
The FLAVR SAVR tomato
The FLAVR SAVR tomato was the first genetically engineered crop product to be commercialized. The research and marketing efforts that produced the FLAVR SAVR tomato resulted in scientific success, a temporary sales success, and then commercial demise. The FLAVR SAVR tomato had been genetically modified to last longer; it stayed healthy at rate where normally tomatoes would rot.
