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Gregor Mendel (1822-1884)
Gregor (baptized as Johann) was raised in the Czech Republic and was socially considered German.During childhood, Mendel gardened for his family farm; and as he grew he attended the Gymnasium (Germany's upper-track educational program). He then went on to study philosophy and agriculture (... a wierd mix I know...). In 1843 he began studying as a priest and by 187, he was a monk. Here he bred pea plants and bees, while studying astronomy and meteorology. He was a true renossance man. -
Mendel's Pea Plants
Mendel started by observing hundreds of different pea plants, looking at two different traits, pod shape and flower color. The options were purple or yellow for color and round or wrinkled for shape. He bought purebred purple and purebred round and mixed it with purebred yellow and purebred wrinkled seeds. These generation is referred to as P -
Mendel's Pea Plants 2
This cross breeding led to the F1 generation which turned out to be all purple and all round. The next step that Mendel took was allowing this F1 generation to self pollinate which resulted in a 3 to 1 ratio of purple to white and a 3 to 1 of round to wrinkled. This generation is called F2 and the genetics used here are refered to as Mendelian genetics. -
Mendel's Pea Plant Meaning
This established the presence of dominant and reccessive alleles. In the pea plants case Purple was dominant and white was reccessive. Dominant always trumps reccessive in Mendelian, this is why the only way to get a recessive trait is if there are two recessive parents (hence why it showed up in the last generation of the experiment). -
Oswald Avery (1877-1955)
He was born in Halifax, Nova Scotia. Avery recieved his AB degree in 1900 from Colgate University. He also earned an M.D. from Columbia.He was a doctor until 1907 when he became a researcher in Brooklyn. He was ill with hyperthyroidism most of his life and in 1936 he was elected a fellow of the American Academy of Art and Sceinces. He died in nashville, Tennessee on Feburary 2, 1955. -
Fredrick Griffith (1879-1941)
Griffith was born in England in around 1879 and he attended Liverpool University. Upon graduation he worked for the Liverpool Royal Infirmary. In 1910 he began working for the government in the ministry of health.He worked a lot with microorganisms, such as pneumococcus. He is said to have enjoyed skiing and was described as kind and shy by many. In 1941 Griffith was killed in a bombing raid of London that hit his building. -
Erwin Chargaff (1905-2002)
He was born in Bukowina, Austria. In 1924 he studied chemistry in Vienna and got his doctorate. He then worked for Yale in organic chemistry but ultimatly returned to Europe. Here he was assistant in charge of chemistry at the University of Berlin and then, due to Nazi occupation of Germany served as a researcher in Paris. Finally, he immigrated to New York in 1935 and took a high level job at Columbia University where he spent most of his career. He had one son, and his wife died before him. -
Alfred Hershey (1908-1997)
He was born in Owosso, Michigan and received his degree in chemistry at Michigan State University. In 1934 he got his Ph.D. at Washington University in Bacteriology. In 1950, he joined the Carnegie research team with his wife Martha. He became director of the Carnegie Institution in 1962. He had one child and a wife. He died in May of 1977 -
Francis Crick (1916-2004)
He was botna dn raised in England. At the University College London he got a degree in physics. He then began his work at Cavendish and soon earned a Ph.D. at University College. During WWII he worked for the allies building various magnets for mines against the axis. He had three children through two marriages and died on July 28, 2004 to colon cancer. -
Rosalind Franklin (1920-1958)
She was born into a Jewish family in Notting Hill, London. Rosalind went to Newnham College in Cambridge and she studied chemistry; this led to her receiving her Ph.D. in 1945. In 1951 she began work at King's College London, doing x-ray diffaction and studying DNA fiber composition. After around three years here, she moved to Birkbeck to further study RNA and DNA. She died of cancer in 1958. -
Martha Chase (1927-2003)
Chase was born and raised in Cleveland, Ohio!!!!!! WOOOOHOOOO!!! She got her degree somewhat late, in 1950 at the College of Wooster. In 1964 she got her Ph.D. from University of Southern California. She was the wife of Alfred Hershey and she suufered a short career due to dementia and eventually passed away in August of 2003. -
Griffith's Mice experiment
Griffith used two strains of pneumococcus bacteria which infect mice – a type S and type R strain. The S strain had a capsule and the R didn't. Upon injection the S strain killed the mice and the R stain injected mice lived. He then heated up the S strain (which killed the internal protein but not the external capsule). -
Griffith's Mice experiment 2
First he injected the heat strained S into the mice and they lived. He then mixed the heat killed S with the R strain and found that all the mice died and he found inside that the mice had live S strain in them. He concluded that the R strain had transformed into live S strain with the help of the heat killed S strain. -
Griffith experiment meaning
He proved that cells have a trnasforming factor that could be DNA -
James Watson (1928- present)
Born in Chicago Illonois, in 1946 Watson began studying genetics and earned his degree from the Univrsity of Chicago. He earned his graduate degree at Indiana University. He worked for the Phage group as a working scientist and later went to Copenhagen University to research. Finally he moved to Cavendish University. In his later years, he is now the director of Cold Spring Harbor Labority and has a family of four. -
Matthew Meselson (1930- )
He was born in Denver Colorado in 1930. He studied chemistry at the University of Chicago in 1951. In 1958 he learned x-ray crystallography. He then taught at Harvard for many years. He also has extensive training in weaponary and nuclear weapons to which his expertice has been contracted on more then one occasion by the US government. -
Avery's experiment
Avery was trying to prove that genes were in DNA not protein so he repeated Griffith's experiment, only this time he destroyed 99.98% of the protein in the S strain and despite this the tranformation still occured. Next he destroyed the DNA and transformation did not occur. -
Avery experiment meaning
Avery proved that almost certainly DNA is the inheritance molecule, not protein but it wasnt concrete (as his extraction process of proteins wasn't perfect). -
Chargaff's experiment
Chargaff and his students collected DNA from various organisms. He then put this in acid that destroyed the phosphodiester bonds, this broke them into individual nucleotides. Then he used Ultraviolet spectrophotometry to analyze the exact amounts of bases (A,T,C,G) that were present in the DNA. This showed an unequal number of bases but the same amount of Adenine and Thymine; as well as the same amount of Guanine and cytosine. -
Chargaff's experiment meaning
His experiments proved that the base pair relationships were between Adenine and Thymine as well as between Cytosine and Guanine. This became known as Chargaff's rule. -
Franklin's experiment
Rosalind used her background in physics as well as chemistry in order to crystilize DNA. This technique involves exposing a crystal to x-ray to produce a diffraction pattern. If a clear pattern is observed scientists can reconstruct the positions of the atoms in the molecules; thus, showing the shape of DNA. She then distinguished between the A and B strands using more DNA crystillization and x-ray imaging. -
Franklins' experiment meaning
Intrestingly Rosalind Franklin's original work on the structure of DNA was finished and submitted one day before the cambridge team of Watson and Crick finished theirs. After her premature death at thirty seven Watson and Crick constantly recognized her contributions to their work and the work of DNA. The impact of Rosalind lies in finding the first structure of DNA and of assisting Watson and Crick in deciding the structure of DNA. She proved DNA was a double helix in shape. -
Wtason and Crick experiment
In my mind Watson and Crick didn't really do too much on their own. They took others work (unpublished work) and manipulated it into working for their agenda. Essentially, Circk had learned how to do x-ray crystallography, however, he never really had to use it becauase Rosalind Franklin (who was much better at it) was doing it at the same time.Watson and Crick had a goal of establishing a three dimensional model of DNA and were funding to do so, however, in 1951 they attempted and failed. -
Watson and Crick experiment 2
Then in 1953 the two received access to Rosalind Franklin's x-ray imageing of DNA (which she didnt grant them permission to use because she hadn't yet published it) and they used it to reform their model. This time the model was made perfectly. Watson and Crick successfully created a three dimensional model of DNA's structure (which is mostly viable today although not entirely). A lot of their work in my opinion, can be credited to Rosalind Franklin though. -
Watson and Crick experiment meaning
Watson and Crick proved many of the same things as Rosaling, they proved DNA to be a double helix, they proved that base pairs are connected with hydrogen bond and that the outer edges with Nitrogen bases also could have hydrogen bonds. They also cemented the idea that DNA strands run anti-parallel. They also helped create fundemental ideas for which three dimensional models should be built upon. -
Hershey and Chase experiment
At this time people were unsure of where genes were in a cell. They were either in the protein or in the DNA. However, genes are far too small to see so the issue was how to recognize the two from each other. To do this, Hershey and his wife decided to use virus' which would infect the host cell and then dump their "genes" into the cell in order to infect it. However, they now had to find a way to distinguish protein from DNA. -
Hershey and Chase experiment 2
In order to seperate the protein from the DNA the scientists made two groups. In one group they radioactively labeled the protein with a radioactive Sulfer solution. In the other, DNA was labeled with radioactive Phosphate. They did this within two groups of identical virus'. Next they had the virus' infect the host cells and then once they had dropped off their "genes" they stuck the test tubes in a centrifuge so that they could seperate the virus' from the cells (which are now infected). -
Hershey and Chase experiment 3
After shaking the two tubes they saw that in the group with the infected protein, the protein had seperated itself from the cell and was on the other side of the cell (if it had infected the cell it should show radioactivity within the cell). Meanwhile, in the group where the DNA was radioactively labeled, the DNA was found within the cell after seperation. -
Hershey and Chase experiment meaning
The Hershey and Chase experiment finally proved and cemented in all scientists minds that genes were located in the DNA and not in protein. A point which was belived but not fully proved until Hershey and his wife. This was their major contribution to DNA structure and understanding. -
Meselson and Stahl experiment
They set out to find which type of DNA replication was actually used. The three viable theories during the time were: conservative, semi-conservative, and dispersive. They began by growing bacteria in a heavier Nitrogen solution and a regular nitrogen solution. After doing this they found tht the DNA ended up in different parts of the tube due to density ( the ones grown in heavier went to the bottom). -
Meselson and Stahl experiment 2
Next they took bacteria and began growing it into heavy nitrogen and then transferred it into normal nitrogen and let it replicate once and then they extracted the DNA. After they centrifuged it they found the DNA in the middle so Conservative was disproved (where it would have to be top or bottom). To disprove dispersive they allowed two replications and they found some DNA in the top which isnt possible in random dispersive process. This meant that DNA replication is semi-conservative. -
Meselson and Stahl experiment meaning
Meselson and Stahl successfully proved how DNA replictes, asserting that it replicates semi-conservatively and proving it as such. This got rid of all the other scientists and allowed scientists to use this knowlege to explain and investiage other topics surrounding replication and allowed them to apply this knowlege to other situations and living things.
