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Discovery of Nucleic Acids
Nucleic Acids were discovered by Friedrich Miescher. He isolated a new compound from the nuclei of white blood cells. He noted it had an acidic nature and called it nuclein. -
Levene's Tetranucleotide
Phoebus Levene determined all of the components of DNA(adenine, guanine, thymine, cytosine and deoxyribose phosphate) and defined the unit including the sugar, the phosphate and the base which he called a nucleotide. He thought it was organized in tetrades, but he was wrong. -
Griffith's transformation experiment
Griffith's experiment, was the first experiment suggesting that bacteria are capable of transferring genetic information through a process known as transformation. -
Avery, MacLeod and McCarty
Their experiments explained Frederick Griffith's results. They determined what actually cause the transformation. Also, they took live rough strain and heat-treated smooth strain and mixed it with one of two enzymes. -
Journal of experimental medicine
Avery, MacLeod and McCarty's experiment was published and there, they suggest that is DNA the one that may be the hereditary material of bacteria and not protein. Also they propose perhaps in higher organisms as well. -
Counting Nucleobases
Erwin Chargaff used a paper chromatography and UV spectroscopy to examine the abundance of the nuclebases and he started to notice something really stange. He examined the amount of the four bases of different living things and he realised that adenine and thymine had almost the same amount and with cytosine and guanine the same. -
Chargaff's rules
Chargaff's rules are that the amount of adenine and thymine are always in balace and the same with cytosine and guanine. -
Hershey-Chase experiments
The Hershey–Chase experiments were a series of experiments conducted that helped to confirm that DNA is genetic material. They proved it with bacteriophages (viruses that affect bacteria) that were the key element for their experiment. -
Watson and Crick inside-out double helix
Watson and Crick came up with the first DNA model that consisted in a double helix with sugars and phosphates at the center and the nucleobases facing the outside. It was totally incorrect. -
Pauling's triple helix
Linus Pauling came up with a triple helix model, with the phosphates and the sugar on the inside and the nucleobases on the ouside. It was mistaken too. -
Rosalind Franklin Photo 51
Rosalind took a lot of amazing photographs of the B form of DNA. She figured out how to see the wet form, the form that exists in the cells. This photo, photo 51, shows the X in the middle that is sign of a double helix. -
Watson and Crick correct double helix
Maurice Wilkins got the photo 51 and managed to get it to Watson and Crick. Now, when they saw the image, they know exactly what it meant and they knew that their model from 1951 was backwards. So, the model builders built the model based on Rosalind's image.
