DNA Timeline


Gregor Mendel


Austrian Monk/Botanist Gregor Mendel discovered Dominant andd Recessive genes through experiments on pea plants, he found that the characteristics of the plant offspring, such as height, showed dominant and recessive behaviour. He also discovers equal segregation, independent assortment and how genetic information is passed through generations.

Friedrich Miescher


Friedrich Meiser indentifies DNA or "Nuclein" as an acidic substance found in cell nuclei. He discovered this by collecting used bandages and scraping the pus from them to isolate a new molecule - Nuclein - from the cell nucleus. He was able to determine that the nuclein was made up of Hydrogen, Oxygen, Nitrogen and Phosphate. There was also a distinctive ratio of Phosphorous to Nitrogen. He was then able to isolate the Nuclein from the other cells.

Sutton and Boveri


The Chromosome Theory of Heredityis suggested by Sutton and Boveri after they both discover, through experiments on sea creatures, that each individual chromosome possessed different qualities. It was also proven that to properly develop the fetus needed to have a full set of chromosomes.

Bateson and Punnett


William Bateson created the word 'Genetics'. Bateson and Reginald C. Punnett discover that some genes are linked and do not show independent assortment. This was also the foundation work for the Punnett Square, named after Reginald C. Punnett.

Sir Archibald Garrod


Sir Archibald Garrod diagnosed the first human disease to be caused by genetics. This disease was called Alkaptonuria. He found that it was rare in the general population but common in first-cousin marriages. This hinted towards the pattern of recessive inheritance that was discovered by Gregor Mendel in his experiments with Pea Plants.

Wilhelm Johanssen


Johanssen formulated the essential distinction between genotype, a genetic constitution of an organism, and phenotype, as an organisms totality on inherited characteristics, through his experiments on Broad Beans.

Thomas H. Morgan


Thomas H. Morgan conducts several experiments on fruit fly eye colour to come up with his theory that certain traits, linked to gender, are found and carried on one of the sex chromosomes (X or Y) . He found this after noticing that there was one white eyed fly, in the midst of 1'237 red eyed flies. He then breeded this fly with a red eyed fly until he had a large amount of white eyed flies. Curiously enough all of the white eyed flies were males. Hence traits that are linked to gender were discovered.

Hermann Muller


Muller used fruit flies, Drysophilia, to show that when specific male fruit flies were exposed to high amounts of radiation and then mated with virgin female fruit flies. Muller was able to artificially induce more then 100 mutations in the fruit flies offspring. This led to the discovery of mutations in cells after a ccertain dosage of Radio activity

John Desmond Bernal


Bernal took x-ray photographs of molecules, amino acids, protiens, steros and nuclearprotiens. All of these were biologically important and set the ground work for may scientists after him.

George Beadle and Edward Tatum


Beadle and Tatum experimented on a bread mold, Neurospara. Neurospara reproduces asexually and only has one set of chromosomes so that any mutation is easily seen. The two men exposed some of the Neurospara to radiation until they had mutant genes. They then crossed the mutant Neurospara with the normal Neurospara and found that some of the offspring were dependent on an amino acid called Arginine and also lost the use of a particular enzyme that helps to produce Arginine. This groundbreaking research showed that genes direct the synthesis off enzymes that control the metabolic process.

Erwin Chargaff


Chargaff shows that there is regularity in the proportions of DNA bases in different species, Guanine approximately equals Cytosine, Adenine approximately equals Thymine, through experiments using paper chromatography.

Rosalind Franklin


Although Franklin was never given credit for her discoveries until after her death, she was a very important person in the discovery of the DNA structure. Her X-ray photos of DNA were described of some of the most beauticul ever taken and she became very close to solving the DNA structure until a picture was shown to James Watson with which he immediately came up with the Double Helix theory. Watson and Crick won a Noble Prize for their discoveries 4 yeas after Franklins death.

Francis Crick and James Watson


The Watson and Crick Double Helix theory was invented. Watson and Crick initially started out using three dimensional models made out of cardboard cutouts and metal sheets to try and understand the theory until Watson made the key insight, that two pairs of complementary bases (Adenine and Thymine, Guanine and Cytosine) would have identical shapes if held together by hydrogen bonds. Two long strands of these bonds would form the double helix which, if separated, would have the ability to copy itself exactly.

Marshall Nirenberg


Nirenberg was the first to crack the genetic code. He did this by adding a simple RNA chain (as they believed protein synthesis took pace in the cytoplasm, where RNA is located) to and E. coli cell with just enzymes and an energy system, along with Amino Acids,one of which is radioactively tagged. Te breakthrough came when they added a strand of RNA made entirely of Uracil to the mix. After leaving the mix in room temperature, Nirenberg discovered the first piece of the genetic code.

Craig Mello


Mello used the nematode worm C. elegans as a model organism to show the mechanism of RNA Interference (RNAi). This is when the presence o a small double stranded RNA (dsRNA) whose sequence matches up with a given gene interfers with the expression of that gene. Many scientists believe that dsRNA which triggers RNAi may be used as drugs.

Francis Collins


Collins was the first to sequence the Human Genome, and found that humans have approximately 20'000 - 25'000 genes. This number was alot less than most scientists predicted. Collins hoped that having an understanding of the human genome would boost the fields of medicine and biotechnology. He also believed that this new discovery could lead to cures for diseases such as Cancer, a mutation of cells and Alzheimer disease, degeneration of the brain.