SCIENCE ACHIEVEMENT

Frederick Griffith
In 1928 Frederick Griffith, British microbiologist, made a series of unexpected observations while performing an experiment with the disease-causing bacteria pneumococcus and laboratory mice. Griffith's experiment dealt with two strains of the bacteria pneumococcus. One was a virulent strain with a smooth polysaccharide coat necessary for infection and colonies of this strain appear smooth. The other was a non-virulent strain with a rough coat that could not cause infection and colonies of the strain appear rough.
Griffith injected one group of mice with the smooth virulent strain and these mice died after a few days. He then injected another group with the rough non-virulent strain and these mice continued to be healthy. Griffith took a heat-killed strain of the virulent bacteria and injected it into mice and observed that they did not die. Griffith's fourth experiment was to inject heat treated, killed, smooth virulent strain mixed with the non virulent rough strain. He injected this mixture and found that after a few days the mice died. The blood of the dead mice showed high levels of virulent pneumococcus. Griffith theorized that some type of transformation takes place from the virulent to the non-virulent strain for it to synthesize a new polysaccharide coat.
GENETIC TRANSFER MATERIAL :DNA

Oswald Theodore Avery

Oswald Avery, Canadian physician and bacteriologist, found that the agent responsible for genetic transferring is the nucleic acid DNA and not protein as most biochemists theorized at the time. In 1944 Avery and his coworkers, McCarty and MacLeod, discovered the "transforming principle."
The Experiment
1.First they treated the bacteria with centafugation(BY CENTRIFUGAL), which eliminates large cellular pieces. The result: bacteria still transformed
2.Added protease(ENZIME), which removes all proteinsThe result: bacteria still transformed
3.Treated the bacteria with deoxyribonuclease(ENZIME), which eliminates all DNA The result: no transformation in the bacteria
The trio concluded that DNA is the cause of transformation, where in this experiment virulence is inherited.

John James Richard Macleod
James Macleod, the Scottish physiologist who is most known for his work on carbohydrate metabolism and insulin, was born on September 6, 1876 in Cluny, Scotland. He was the son of Reverend Robert Macleod. After his family moved to Aberdeen he attended Aberdeen Grammar School and then Marischal College of the University of Aberdeen to study medicine. In 1898 he obtained his medical degree with honors and was awarded the Anderson Traveling Fellowship. That year he published his first paper which was on the phosphorus content of muscle.
Macleod worked for a year at the Institute for Physiology at the University of Leipzig, Germany. The following year he was made demonstrator of Physiology at the London Hospital Medical School, and in 1902 was given the position of Lecturer in Biochemistry at the same school. That same year he was granted the McKinnon Research Studentship of the Royal Society until 1903 when appointed Professor of Physiology at the Western Reserve University at Cleveland, Ohio. In 1905 Macleod first became interested in carbohydrate metabolism especially in patients with the disease diabetes. He published thirty-seven papers on carbohydrate metabolism and an additional twelve papers on the experimentally produced glycosuria. He published a textbook on diabetes mellitus, the most common form of diabetes, which is the result of the body's failure to process the sugar glucose. When glucose can not be correctly stored and used, the level of glucose with the bloodstream rise, which cause serious complications. Diabetes mellitus was fatal during this time period.
During the winter session of 1916, Macleod was Professor of Physiology at McGill University, Montreal. In 1918 he was elected Professor of Physiology at the University of Toronto, Canada along with Director of the Physiological Laboratory and Associate Dean of the Faculty of Medicine. It was that this university that he did his work with insulin. Macleod and his research team found that the pancreas secretes insulin, which regulates the amount of glucose in the body's cells. Research revealed diabetes mellitus to be a failure of the pancreas to produce insulin. Frederick Banting, a Canadian surgeon came to Macleod in 1921 and asked for help in isolating insulin. He gave Banting laboratory access, dogs for experiment subject and medical student Charles Best as an assistant. Banting and Best performed a series of experiments, surgically changing the dog's pancreas. They extracted the insulin producing cells and then removed the insulin from these cells. They injected the insulin into the dog that was now artificially made diabetic. Observations showed that the injections controlled glucose levels in the dogs. Macleod and Canadian biochemist James Bertram Collip worked with Banting and Best to refine methods of removing and purifying insulin. In 1922, Banting and Best injected their insulin into a fourteen year old diabetic boy, which successfully treated his condition. Macleod publicly announced their discovery in February of 1922 and the patent for manufacturing of the pancreatic extract was approved. All financial proceeds of the patent went to the British Medical Research Council and the discoverers were given no payment. Banting and Macleod were jointly awarded the 1923 Nobel Prize for physiology or medicine. They both shared the prize money with Best and Collip.
Macleod was appointed Regius Professor of Physiology at the University of Aberdeen in 1928 and he held that position along with Consultant Physiologist to the Rowett Institute for Animal Nutrition until his death. Throughout his life, Macleod wrote eleven books and monographs. In 1932 he returned to his research and work on the possibility that the central nervous system plays a role in the cause of hyperglycemia. After experimenting on rabbits, Macleod concluded that stimulation of gluconeogenesis in the liver occurred via the parasympathetic nervous system. He also did work on air sickness, purine bases and electric shock. James Macleod died March 16, 1935.

Alfred Day Hershey
Alfred Hershey, the American geneticist, was born December 4, 1908 in Owosso, Michigan. He attended Michigan State University and in 1930 received his B. S. in chemistry and 1934 his Ph. D. in bacteriology. In that same year he was given the position of research assistant at the Department of Bacteriology of Washington University, St. Louis, Missouri. Hershey was promoted to instructor in 1936, assistant professor in 1938 and associate professor in 1942.
Throughout the 1940's Hershey worked with Italian microbiologist Salvador Edward Luria and German physicist Max Ludwig Henning Delbruck performing experiments with bacteriophages, which are viruses that infect bacteria. They organized the "Phage Group", a team of bacteriophage researchers who met every year at Cold Spring Harbor to discuss their work and advances. While Hershey and Delbruck were working together in 1946, they observed that when two different strains of bacteriophages have infected the same bacteria, the two viruses may exchange genetic information. They then produce offspring with different infective natures than either parent had. This was the first example of GENETIC RECOMBINATION in viruses.
He moved to Cold Spring Harbor, New York to join the Carnegie Institution of Washington's Department of Genetics in 1950. In 1952, Hershey and American geneticist Martha Chase performed their famous "blender experiment." Using a kitchen blender, they separated the protein coating from the bacteriophage's nucleic acid core. They injected nucleic acid into the bacterial cell and found that the acid itself caused replication and transmission of genetic information, not its protein components. This proved that genes are made of the nucleic acid DNA. One year later James Watson and Francis Crick announced the double-helix structure of DNA and a theory on how genetic material is passed. He then became director of the Carnegie Institution, renamed Genetic Research Unit at Cold Spring Harbor in 1962. Hershey's later research helped the development of vaccines for polio, measles and mumps. Hershey was awarded the 1969 Nobel Prize in physiology or medicine, along with Luria and Delbruck, for their discovery on the replication of viruses and their genetic structure. He retired from active research in 1972 but was a constant figure around the lab until his death in May of 1997.

SOURCE FROM:
http://library.thinkquest.org/20465/griffith.html
http://library.thinkquest.org/20465/avery.html
http://library.thinkquest.org/20465/macleod.html
http://library.thinkquest.org/20465/hershey.html