-
Friedrich Miescher
Miescher discovered DNA by using white blood cells from bandages of hospital patients. He bathed the cells in warm alcohol. By bathing them in alcohol, lipids were removed. Then enzymes were let loose on them to digest protein. What was left was a substance Miescher called nuclein (it would be later known as nucleic acid).He contributed the fact that DNA was a distinct molecule different from protein found in the nucleus. -
Friedrich Miescher
His discoveries led to further experiments done by other scientists in attempt to analyze this new concept of DNA.Earlier people thought that cells were mainly made of proteins, but Miescher argued that cells were made of things other than protein. Without his discovery, we would never had known what DNA was. -
Edwin Chargaff
Chargaff collected many DNA samples and analyzed their base composition.By looking at them, he discovered that pyrimidines (A and G) equal purines (T and C).This became known as Chargaff's rules. He also discovered that the amount of nitrogenous bases depends on the species the DNA came from.He contributed information regarding the nitrogenous bases and the amount of each organism. By contributing this information, we have a better understanding about the approximate amount of each base in DNA. -
Edwin Chargaff
Chargaff's work disproved Levene's hypothesis that DNA was made up of equal amounts of each of the 4 bases. This changed the way we saw nitrogenous bases. -
Rosalind Franklin
Franklin discovered that DNA had a double helix shape. While working with a graduate student, Franklin used 2 forms of DNA on X-ray images. One form of the DNA was dry and the other was wet. They were arranged differently for her chromatography. The wetter DNA showed a helix structure with 2 clear strands. She eventually concluded that nitrogenous bases were near the center of the DNA molecule. She also concluded the angle of the X suggests 2 strands of DNA in the structure. -
Alfred Hershey and Martha Chase
Hershey and Chase did an experiment developing 2 batches of T2 bacterio phage. One was developed in the presence of radioactive phosphorus (found in DNA) and the other in the presence of radioactive sulfur (found in protein). They blended the batches causing a disturbance. Then it was easy to detect whether protein or DNA made it into the bacteria. Their results showed that DNA had in fact made it inside the bacteria. They discovered that genetic material of a virus is DNA and not proteins. -
Rosalind Franklin
Her x shaped pattern shows DNA strands twisted around each other in a helix. Franklin was the first to make conclusions about the DNA structure. Her clues in her pattern enabled Watson and Crick to build a 3D DNA structure and explain specific properties. -
Alfred Hershey and Martha Chase
This changed the way other scientists conducted their experiment regarding DNA. Their discovery helped people better understand what genetic material was made of. Without this information, future scientists' results would be inaccurate. -
James Watson and Francis Crick
Using cardboard and wire, Watson and Crick attempted to explain DNA's properties in a 3D model, but they had no success. After Watson saw Franklin's X-Ray pattern of the DNA structure and spoke to Chargaff in regards to base pairing, he mended his and Crick's structure. The pair later published their discovery in a book which described the model as a double helix with 2 strands of nucleotide sequences wrapped around each other. -
James Watson and Francis Crick
They contributed a detailed 3-D model of DNA. They said that DNA replicates by splitting down the middle and building 2 ladders by matching complementary halves. And also mutations come from a change in the order of bases along the ladder. Their discovery constructed what DNA was made of and explain Chargaff's rule for base pairing and what held together the 2 strands of DNA. With their model, we were able to understand how DNA functions and how that relates to our genetic information. -
Matthew Meselson and Franklin Stahl
Meselson and Stahl grew E. coli bacteria and took DNA samples from each generation. Using the samples, they measured the density of DNA using density gradient centrifugation which separates molecules into bands by spinning them at high speed in the presence of another molecule. Their experiment demonstrated that DNA replicates semi- conservatively (one strand is new and one strand is old). They contributed a visual model of the semi-conservative model. -
Matthew Meselson and Franklin Stahl
They proved why other models were inaccurate and the semi-conservative model is a better representation. Their experiment helped people better understand models that appropriately demonstrated DNA strands.
