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DNA Timespan
Timespan of the DNA Timeline -
Frederick Griffith
Frederick Griffith injected mice with the S and R strains of Pneumococcus (Bacteria that causes Pneumonia). Those who were injected with the S strand died, and those with the R did not. He began to wonder if one strand could change into the other. So, he heated up the S strain, and sure enough, when it was injected into a mouse, it did not die. But, when he mixed the R and S (Heated) strains together and injected it, the mouse died. He concluded there must be some kind of transformer involved. -
Frederick Griffith (Small Addition)
I coudl not fit this part in. But, when Frederick Griffith injected the mouse with the heated S strain and the R strain, after it was dead, he could recover the live S strain from the mouse.
(Sorry, this site limits you on space) -
Oswald Avery (Breakthrough Discovery)
Intrigued by Frederick Griffith's work, he wanted to find out the identity of the "transformer." He used test tubes instead of mice. First, he took the S strain of Pneumococcus, and used enzymes to remove the sugar coating, and protein. Then he islolated the RNA and DNA, and placed them in a water solution. They destroyed the RNA, and it still transformed. But when the DNA was removed, it did not transform. So, he concluded that DNA was the transformer. -
Watson and Crick (Continued 2)
... right form. Wherever there was aa A for example, there was a T on the opposite side. Same with C & G. This is a massive contribution to biology, and helped clear up many things. -
Erwin Chargraff
Erwin Chargraff thoguht that there was more to DNA than what was previously thought. He took DNA from 4 different organisms, and measured the levels of each of the 4 nitrogenous bases. The results he discovered were that the amounts of Adenine and Thymine were very close together, and that the amounts of Guanine & Citosine were practically the same. He disproved Levene's tetranucleotide theroy, that the amounts of A, T, G, & C are constant throughout organisms. Instead, they are arranged so... -
Erwin Chargraff (Continued)
all living organisms. Instead there should be close to equal amounts of A & T, and equal amounts of G & C. But, he could not make senes of the perhaps meaningless regularities -
Rosalind Franklin
Rosalind Franklin discovered the 3-dimensional structure of DNA. She did this by studying a x-ray defraction pattern of DNA. She worked with Maurice Wilkins to create them. From them, she was able to calculate the dimensions of DNA, which eventually lead to the discovery of DNA's 3-D structure -
James Watson and Francis Crick
Watson and Circk werer the first to publish and accurate model of the DNA molecule. Phobeous Leneve first said that DNa is made of a phosphate group linked to a deoxyribose sugar, which is connected then to one of four nitrogenous bases. (Adenine (A), Guanine (G), Cytosine (C), & Thymine (T). Nucleotide are linked in a series, but Levene his tetranucleotide theory was wrong. If it was correct, the DNA would not be intelligent enough to carry info. It actually made sense that the nucleotides... -
Watson and Crick (Continued)
... changed, so that the DNA could store information. Chargaff's base ratios (A=T, G=C) were important for them. Then following Linus Paulin, they used X-Ray crystallography to "scan the DAN. Rosalind Franklin, and Muarice Wilkins were given these to look at. They were able to calculate the basic dimensions of a DNA molecule. This allowed them to finally decide that the double-helix was the only logical way of DNA structure. This discovery was published in a science journal called Nature. -
Alferd Hershy & Martha Chase
Herchey and Chase set out to discover what caused the transformation of bacteria with phage. Knowing that DNA is high in phosphorus, and proteins are high in sulfur. They used radioactive sulfur and phospohrus to label the DNA and proteins. In 2 parallel experiments, they poured the solutions into the bacteria host, and then waited long enough for the phage to attatch to the bacteria. Then they shook it up in a blender. After that, they spun it around in a centrifuge to separate the bacteria and -
Alfred Hershey and Martha Chase (Continued)
... separate the bacteria and phage. When the sulfur tube is looked at, the bacteria did not have radioactive proteins. Therefore, the phage coat was not used in the bacteria to make new phage particles. The phosphorus was the exact opposite, with the bacteria having radioactive phosphorus. Therefore, they concluded, the DNA was used to make new phage in the bacteria. And from that, they concluded that DNA holds the genetic material.
