Gregor Mendel
Oswald Avery
Colin MacLeod
Maclyn McCarty
Alfred Hershey
Arthur Kornberg
James Watson
Frederick Sanger
Walter Gilbert
Maclyn McCarty
Maclyn McCarty
National Library of Medicine
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Key accomplishments: DNA


Gregor Mendel

Experiments with peas lead Austrian monk Gregor Mendel to discover that certain traits are inherited in varying proportions, depending on whether they are recessive or dominant.


Frederich Miescher
First DNA Isolation

Swiss physician Frederich Miescher isolates DNA from cells. Miescher calls it "nuclein." Later, it becomes known as nucleic acid.


Wilhelm Johannsen
The Term "Gene" is Coined

German scientist Wilhelm Johannsen names the Mendelian unit of heredity "gene," from the Greek word, "give birth to."


Frederick Griffith, Jr.
Gene Transformation Suggested

British microbiologist Frederick Griffith's experiments with pneumococcus prove that a "transforming principle" allows genes to transfer from one bacterium to another.


Oswald Avery, Colin MacLeod, and Maclyn McCarty
DNA Transforms Cells

American geneticists Oswald Avery, Colin MacLeod, and Maclyn McCarty prove that DNA is the "transforming principle"—the vehicle for passing hereditary information through generations.


Erwin Chargaff
Chargaff's Rule

Austrian-American biochemist Erwin Chargaff discovers equal amounts of adenine and thymine, and cytosine and guanine, a distinctive pattern of base-pairing regularities in DNA. In 1950 he publishes his findings.


Alfred D. Hershey and Martha Chase
Genes are Made of DNA

American geneticists Alfred Hershey and Martha Chase demonstrate that only the DNA of a virus needs to enter a bacterium to infect it, proving that genes are made of DNA.


Arthur Kornberg and Severo Ochoa
Polymerase and RNA Identified

American biochemist Arthur Kornberg and Spanish born biochemist Severo Ochoa share the Nobel Prize in Physiology or Medicine for their discovery of polymerases in the biologic synthesis of deoxyribonucleic acid and ribonucleic acid.


Sydney Brenner, François Jacob, and Matthew Meselson
Cellular Messengers: mRNA

South African chemist Sydney Brenner, French biologist François Jacob, and American geneticist Matthew Meselson show that short-lived RNA molecules, which they called messenger RNA (mRNA), carry the genetic instructions from DNA to structures in the cell called ribosomes, (the site of protein synthesis).


James D. Watson and Frances H. Crick
DNA structure is a double helix

In 1953, James Watson and Frances Crick propose a three-dimensional model for the structure of DNA: a double helix molecule formed by two chains, each composed of alternating sugar and phosphate groups, connected by nitrogenous bases. Watson and Crick (with British biophysicist Maurice Wilkins) are awarded the 1962 Nobel Prize in Medicine or Physiology.

The Frances Crick Papers


Werner Arber and Hamilton Smith
Role of Restriction Enzymes

Swiss molecular biologist Werner Arber shows how specialized enzymes can cut DNA into short strands. These enzymes are subsequently dubbed "restriction enzymes." In 1970, American molecular biologist Hamilton Smith and colleagues determine that restriction enzymes can cut DNA molecules at precise and predictable locations. Arber shares the 1978 Nobel Prize in Medicine or Physiology with Smith and American biologist Daniel Nathans.


Frederick Sanger, Alan Coulson, Alan Maxam, and Walter Gilbert
DNA Sequencing Methods Developed

In the 1960s and 1970s, British scientists Frederick Sanger and Alan Coulson, and Alan Maxam and Walter Gilbert in the United States, develop DNA sequencing techniques. Automated equipment makes DNA sequencing a speedy, routine laboratory procedure. Gilbert and Sanger win the 1980 Nobel Prize in Chemistry for their work.

David Botstein, Ronald W. Davis, Mark Skolnick, and Ray White
Restriction-Fragment-Length Polymorphism (RFLP) proposed

American geneticist David Botstein, biochemist Ronald W. Davis, population geneticist Mark Skolnick, and biologist Ray White publish a paper on their theory that restriction fragment-length-polymorphisms (RFLPs) can be used to produce a linkage map of the human genome and to map the genes that cause disease in humans.


Alec Jeffreys
Variable Numbers of Tandem Repeats

British geneticist Alec Jeffreys finds that multiple copies of short nucleotide sequences, 3 to 30 base pairs long, are repeated one after another, 20 to 100 times [e.g., GACTGACTGACT]. These groups of repeat sequences, called minisatellites or VNTRs (variable number of tandem repeats), are now known to be widely scattered throughout the human genome. The number of these regions at different loci are different in each individual.


Alec Jeffreys
Short Tandem Repeats in DNA Analysis

Geneticist Alec Jeffreys develops short tandem repeat (STR) DNA typing, which the forensic community adopts as its standard.