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He discovered the parts of DNA: sugar, phosphate and base. He called this unit a nucleotide. But he thought DNA was too simple to be genetic material. -
He worked with two types of pneumonia bacteria (smooth = deadly, rough = harmless). He found transformation: rough bacteria became deadly when mixed with dead smooth bacteria. -
They repeated Griffith’s experiment. They used enzymes to destroy proteins or DNA. Only when DNA was destroyed, transformation did not happen. So DNA was the genetic material. -
He made a triple helix model with phosphates inside. This was also wrong, like the model of Watson and Crick -
They made a model of DNA with bases outside and phosphates inside. This model was wrong. -
They used viruses, like phages, with radioactive labels. Protein did not enter bacteria, but DNA did. This showed DNA is the genetic material. -
He counted nucleobases in many organisms. He found that A = T and C = G. These are known as Chargaff’s Rules. -
She took X-ray photos of DNA. Photo 51 showed the double helix structure. Her data was very important then and nowadays -
Using Franklin’s data, they built the correct model: DNA is a double helix with bases inside and sugar-phosphate outside.