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1902: Orderly Inheritance of Disease Observed
Archibald Garrod observes that the disease alkaptonuria is inherited according to Mendelian rules. -
1869: DNA First Isolated
Friedrich Miescher isolates DNA for the first time.
Miescher isolated a material rich in phosphorus from the cells and called it nuclein. He found nuclein in other types of cells as well, including salmon sperm. -
1909: The Word Gene Coined
Danish botanist Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity. -
1941: One Gene, One Enzyme
George Beadle and Edward Tatum, through experiments on the red bread mold Neurospora crassa, showed that genes act by regulating distinct chemical events - affirming the "one gene, one enzyme" hypothesis. -
1944: DNA is "Transforming Principle"
Oswald Avery, Colin MacLeod, and Maclyn McCarty showed that DNA (not proteins) can transform the properties of cells, clarifying the chemical nature of genes -
1955: 46 Human Chromosomes
Joe Hin Tjio defined 46 as the exact number of human chromosomes.He prepared metaphase spreads that showed the chromosome arrays particularly neatly. He found that all unbroken cells had 46 chromosomes. -
1956: Cause of Disease Traced to Alteration
In 1956, Ingram discovered that a specific chemical alteration in a hemoglobin protein - the substitution of valine for glutamic acid in the sixth amino acid in beta globin - is the root of the disease. -
1961: First Screen for Metabolic Defect in Newborns
In 1961, Robert Guthrie, a doctor and bacterial scientist at the University of Buffalo Children's Hospital, developed a way to test whether newborn babies have phenylketonuria (PKU), an inability to digest the amino acid phenylalanine. -
1966: Genetic Code Cracked
Marshall Nirenberg, Har Khorana and Severo Ochoa and their colleagues elucidated the genetic code - showing how nucleic acids with their 4-letter alphabet determine the order of the 20 kinds of amino acids in proteins. -
1975-77: DNA Sequencing
Sanger and his colleagues developed a slightly different protocol for sequencing DNA compared with Maxam and Gilbert. Sanger's method, where a marker attaches to the growing ends of DNA chains. -
1987: First Human Genetic Map
The first comprehensive genetic map of human chromosomes was based on 400 restriction fragment length polymorphisms (RFLPs). -
1990: Launch of the Human Genome Project
The DOE was interested in studying the human genome as a way of aiding the detection of mutations that nuclear radiation might cause. In 1990, DOE and NIH published a plan for the first five years of what was projected to be a 15-year project.
Goals: mapping the human genome and determining the sequence of all 3.2 billion letters in it; developing technology for analyzing DNA; and studying the ethical, legal and social implications of genome research.
