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Milestones in DNA history

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1. The Double Helix structure of DNA was first described by :
• Watson and King
• James Watson, Francis Crick and Maurice Wilkins
• Oswald Avery
• Peter Mitchell
Answer: James Watson, Francis Crick and Maurice Wilkins
The Double Helix structure of DNA is one of the most significant discoveries of all time. James Watson, Francis Crick and Maurice Wilkins received a Nobel Prize for the Double Helix model of DNA in 1962 ! Another important figure, without whom this discovery would not have been possible was Rosalind Elsie Franklin. Unfortunately, Franklin died at the age of 37 from Ovarian Cancer just four years before the Nobel prize was awarded to Watson, Cricks and Wilkins.It is a tremendous shame that Franklin did not receive due credit for her essential role in this discovery, either during her lifetime or after her untimely death...


2. The scientist who first showed that genetic material is a heat stable chemical is :
• Franklin Griffith
• Erwin Chargaff
• Friedrich Miescher
• Oswald Avery
Answer: Franklin Griffith
This famous breakthrough resulted from an experiment carried out by Franklin Griffith in 1928. He discovered that genetic information can be transferred from heat-killed bacteria cells to live ones.


3. The scientist who identified the transforming agent in Griffith's famous experiment (1928) as DNA was :
• Erwin Chargaff
• Friedrich Miescher
• Peter Mitchell
• Oswald Avery
Answer: Oswald Avery
In 1944, Oswald Avery, and his colleagues Maclyn McCarty and Colin MacLeod identified the transforming agent in Griffith's experiment as DNA.



4. The scientist who reported that DNA composition is species specific was :
• Sidney Brenner
• Herbert Boyer
• Erwin Chargaff
• Hamilton Smith
Answer: Erwin Chargaff
In 1949, Erwin Chargaff, a biochemist, reported that the amount of DNA and its nitrogenous bases varies from one species to another. He also found that the amount of adenine equals the amount of thymine, and the amount of guanine equals the amount of cytosine in DNA from every species !


5. Proof of the model of DNA replication suggested by Watson and Crick came from the experiments of :
• Stanley Cohen and Herbert Boyer
• M. S. Meselson and F. W. Stahl
• Sidney Brenner and Francis Crick
• George Beadle and Edward Tatum
Answer: M. S. Meselson and F. W. Stahl
The experiment performed by Meselson and Stahl is sometimes referred to as "The most beautiful experiment in biology." The experiment showed that DNA replication is semi-conservative.
Trivia : Meselson's external advisor for his thesis was Richard Feynman ! !


6. The scientist(s) who developed a technique to sequence DNA and later won a Nobel prize for their achievement in 1980 is(are) :
• Arnold Levine and Gerald Edelman
• Harold Varmus and Rodney Porter
• Clara Bloomfield
• Walter Gilbert and Frederick Sanger
Answer: Walter Gilbert and Frederick Sanger
Dr Walter Gilbert of Harvard University and Frederick Sanger developed a method for decoding DNA. His technique sparked off the biotech revolution because it enabled researchers to begin cloning genes.


7. The scientist who created the first recombinant DNA molecules :
• Howard Temin
• James Shapiero
• Ian Wilmut
• Paul Berg
Answer: Paul Berg
In 1972, Paul Berg combined the DNA of two different organisms, thus creating the first recombinant DNA molecules. He developed a technique for splitting DNA molecules at selected sites, attaching segments of the molecule to the DNA of a virus, and then introducing it into bacterial cells. The foreign DNA was incorporated by the host, which then produced proteins not usually found in the host. This joining of two pieces of DNA from different species is called recombinant DNA. The process is a cornerstone of genetic engineering. He won a Nobel Prize for his work in 1980.


8. The first organism ever to be cloned from adult cells was :
• Dolly, the sheep
• A cow
• Northern Leopard frogs
• Tadpoles
Answer: Dolly, the sheep
On July 5, 1996, Dolly (a sheep), the first organism ever to be cloned from adult cells, was born. Earlier, clones of other organisms such as cows and frogs had been created from early embryo cells and not adult cells.


9. One of the surprises uncovered by the Human Genome project was the surprisingly small number of genes that humans possess. This number is approximately :
• 10000
• 80000
• 35000
• 60000
Answer: 35000
The Human Genome project revealed that humans have approximately 35000 genes which is lower than expected. Even an insect as simple as the fruitfly has as many as 20000 genes.


10. Robert Holley, Har Gobind Khorana, and Marshall Nirenberg shared the Nobel prize for medicine in 1968 for their contribution to DNA reasearch, which was :
• the discovery of the structure of DNA.
• the elucidation of protein synthesis.
• the discovery of the lac(tose) operon.
• the discovery of the presence of DNA which could not be expressed.
Answer: the elucidation of protein synthesis.
In 1968, Robert Holley, Har Gobind Khorana, and Marshall Nirenberg shared the Nobel prize in medicine for the elucidation of the process of protein synthesis. They also discovered which amino acids are designated by each of the three letter codes. They also determined that the translation of the code was universal amongst different organisms.


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