-
Friedrich Miescher
He attempted to isolate cells from the pus of a surgical bandage. He managed to isolate leucocytes, which were filtered through a sheet that removed cotton fibers. Then he separated the nuclei from the cytoplasm. That has not been done before and he had to develop new protocols. The new protocol let him isolate nuclein in quantities. He realized that the new substance was not a protein and he termed the substance nuclein,which is still used in the name for deoxyribonucleic acid (DNA). -
Erwin Chargaff
Erwin Chargaff discovered that the percentage of adenine and thymine bases are almost equal in any sample of DNA. He then discovered that guanine and cytosine are also equal, this is known as Chargaff's rule. He analyzed the base composition of DNA in cell to discover that purines and pyrmidines are equal. Chargaff's rule helped Watson and Crick come to the right conclusion of their model of the double helix by realizing why adenine equaled thymine and guanine equaled cytosine. -
Rosalind Franklin
Franklin used a technique called X-ray diffraction to help her discover the structure of DNA. she purified DNA, then stretched the DNA fibers in a thin glass tube so that the stands would be parallel. Next she used a powerful X-ray beam on the DNA and recorded the scattering pattern of the x-ray film. Her x-ray pattern carries important clues that DNA is in a form of a helix, and thanks to Franklin's work, Watson and Crick were able to publish their model of the DNA double helix. -
Alfred Hershey and Martha Chase
Hershey and his assistant Chase wanted to show that proteins carry genetic information.They used the T2 bacteriophage for their first experiment to deliver genetic material, but their experiment did not work. Their experiment did not work because They wanted to demonstrate that at least a portion of the phage’s protein mass was transferred to the interior of the bacterium. They tried several other experiments and their last experiment showed how DNA was actually the carrier for genetic material. -
James Watson and Francis Crick
James Watson and Francis Crick both wanted to understand the structure of the DNA. They used cardboard and wire to create a 3-dimensional model of the DNA to help them discover the double helix. They relived that the double helix accounted for Franklin's X-ray pattern. The double helix model also explains Chargaff's rule of base pairing and how the two strands of DNA are held together. Their model can tell us how DNA can function as a carrier of genetic information. -
Meselson & Stahl
They discovered that the DNA replication is semiconservative. Watson and Crick previously suggested that their DNA model would be how replication occurs, but the proof of the model actually came from the experiments of Meselson and Stahl. They grew E. coli (bacteria) to help them discover the DNA replication. After growing the E. coli for several generations, they found that the DNA cells were heavier than normal due to the atoms. As a result of this, the cells split and were almost identical.
