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Gregor Mendel's experiments with peas
Starting in 1857 a monk named Gregor Mendel began experimenting with pea plants to study traits passed on from one generation to the next. Mendel was one of the first to study genetics. -
DNA First Isolated
Friedrich Miescher was a Swiss scientist; he was the first person to isolate DNA. Miescher isolated nucleic acids from the nuclei of white blood cells. -
Mitosis first observed
Walther Flemming observed chromosome movement and cell division by observing salamander embryos. He came up with many terms (such as prophase, metaphase and anaphase) to describe the various stages of mitosis which are still used today. -
Chromosome Theory of Heredity
Walter Sutton, an American geneticist, was the first to observe meiosis; which he did in 1902. Sutton developed what is now known as the Boveri-Sutton chromosome theory, which states that the Mendelian laws of inheritance can be applied to chromosomes. -
The word “gene” is first used by Wilhelm Johannsen
Danish botanist Wilhelm Johannsen first used the term “gene” as a name for Mendelian units of heredity. Johannsen also recorded the differences between a genotype and a phenotype. -
Strong evidence provided that genes are made of DNA
Martha Chase and Alfred Hershey conducted experiments that prove that only the DNA of a virus is needed to infect a bacterium. Their work did much to reinforce the earlier claims made by Avery that genes are made of DNA. -
Francis Crick and James Watson discover that the structure of DNA
In the 1950s, much was already known about DNA; however, its exact structure was still unknown. Francis Crick and James Watson used models made from cardboard and metal scraps to discover that the structure of DNA was a double helix. -
Exact number of human chromosomes discovered
Joe Hin Tjio, a researcher for the National Institutes of Health, found the exact number of human chromosomes to be 46. -
Genetic code cracked
Marshall Nirenberg, Har Khorana and Severo Ochoa “cracked” the genetic code by demonstrating how nucleic acids, with a 4-letter alphabet, can determine the order of the 20 different kinds of amino acids in proteins. They discovered how mRNA reads codons (three nucleotides); this creates more than enough variety, with the 4 letters in amino acids, to code for the 20 different kinds of amino acids. -
Human Genome Project launched
In 1900 the Human Genome Project (HGP) was launched with the purpose of mapping and sequencing the human genome. The Human Genome Project was completed in April, 2003.
