The History of DNA

This week in AP Biology we talked about all of the different scientists and other geniuses that proved certain characteristics of DNA. The first was T.H Morgan and he worked with fruit flies and saw that genes are on chromosomes. The second person was Fredeirick Griffith and he worked to try and find a cure for pneumonia. From doing this he saw that harmless live bacteria mixed with heat-killed infectious bacteria caused disease in mice. Griffith called this substance that passed from dead bacteria to live bacteria the transforming factor or transformation. Avery, McCarty, and Macleod also looked for this transforming factor by purifying both DNA and proteins from streptococcus pneumonia bacteria. They found that when they injected protein in bacteria that there was no effect, but when they injected DNA in bacteria, they saw that it transformed harmless bacteria into virulent bacteria. Hershey and Chase, yet more scientist that worked with the transforming factor, but Hershey and Chase confirmed that DNA is the transforming factor by doing the blender experiment. They worked bacteriophage which is a virus that infects bacteria. They grew phage viruses in 2 media radioactively labeled. This blender experiment is how they confirmed that DNA is the transforming factor. Erwin Chargaff saw that all 4 bases of DNA are not in equal amounts. Adenine is 30.9%, Thymine is 29.4%, Guanine is 19.9% and Cytosine is 19.8% of a humans DNA. Watson and Crick simply developed the double helix structure of DNA. A woman named Rosalind Franklin is what gave Watson and Crick to make the double helix structure. And the final two people we discussed is Meselson and Stahl. Meselson and Stahl proved that DNA is semi conservative which is when two strands of DNA separate and one strand is a template and the new strand is laid down. All of these scientist are very important because of their discoveries about DNA.