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Friedrich Miescher
Miescher discovered a substance in the nuclei of white blood cells that contained both phosphorous and nitrogen. The substance was first called nuclein because he thought it came from the cell nuclei. It later became known as nucleic acid in 1874, after Miescher had separated it into protein and acid components. This substance is now known as deoxyribose nucleic acid (DNA). -
Frederick Griffith
Griffith studied two strains of bacteria, one which would kill a mouse known as virulent, the other which would not is known as avirulent. He found that mice injected with the heat-killed virulent bacteria or the living avirulent remained in good health. He also observed mice injected with a mixture of the two died. He concluded that there was a chemical changing principle that had been transferred from the virulent bacteria to the avirulent bacteria and changed it, causing it to kill the mice. -
Barbara McClintock
discovered that genes could be mobile, her studies of chromosome breakage led her to discover a chromosome breaking locus. -
Oswald Avery, Maclyn McCarty and Colin McCleod
These three scientists set out to prove Griffith's "transforming principle". They acquired large amounts of the same heat-killed virulent bacteria that Griffith had used and separated its cellular components from the "transforming principle". They got very small, but pure amounts of it. They put the "transforming principle" through multiple tests to identify its composition. They concluded it was most likely DNA, but Avery was skeptical that it could be made up of proteins. -
Erwin Chargaff
He discovered that in all DNA there are a few rules. Frist, the amount of adenine and thymine are always equal. Second, the amount of guanine and cytosinr are always equal. Finally, all pyrimidines in toatal are equal to the toatl number of the purines. He was able to observe this by seperating the DNA out of different nuclei. He started this investigationg in 1944, and it helped other scientist to discover DNA's molecular structure. -
Alfred Hershey and Martha Chase
They studied the viruses that attacked bacteria, such as phages, which are viruses that are parasitic to bacteria. The phages have both proteins and DNA, and when they attach to a host cell they inject it with a substance that gives the cell instructions to make more phages. They exposed two different groups of phages to two radioactive elements to find whether the injected substance was proteins or DNA. The injected substance turned out to be DNA because it had the element only found in DNA. -
Rosalind Franklin and Maurice Wilkins
Franklin and Wilkins discovered the size, shape and location of the phospates in dehydrated and hydrated versions of DNA. They discovered this after Franklin had taken pictures of the DNA with a x-ray. The model they had used was hydrated and dehydrated DNA. After the photos were taken though, Wilkins showed them to another scientist who later claimed he discovered the shape of DNA, the double helix. -
Linus Pauling
After studying proteins and amino acids for many years, he developed an interest in DNA. Pauling thought DNA was a helix and was also three demensional. In 1953, Pauling and Robert Corey published what thy thought DNA looked like, which was three strands wrapped aroud each other like a rope. Basically, a triple helix almost. They came to this conclusion by looking at nuclei from cells that were important to life. This inspired James Watsons and Francis Cricks design of DNA, the double helix. -
Period: to
DNA Discovery
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James Watson, and Frances Crick
Discovered the double helical structure of DNA. Marked a milestone in science history and gave rise to molecular biology. they used works from previous scientists to prove the theory aswell -
Meselson and Stahl
Supported Watson and Crick's discoveries that DNA was semi-conservative. Using an Isotope of Nitrogen to see the difference between parent and daughter, he could see the copied strands of DNA after replication. -
Fredrick Sanger
Worked on solving DNA sequencing, dideoxy method was discovered, deemed the "rapid way of sequencing DNA" -
Paul Berg
DNA Splicing of a bacteria virus known as lambda resulting in the first man-made recombinant. -
Craig Venter
Independently mapped and sequenced human DNA, he helped on the human genome project and created the EST method of finding genes -
Kary Mullis
Invented the Polymerase chain reaction, a simple technique that allows a specific stretch of DNA to be copied billions of times in only a few hours. PCR requires a template of DNA to base off of and two oligonucleotide primers.
