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History of The discovery of DNA

History of The discovery of DNA

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History of The discovery of DNA. Johann Friedrich Mieschner 1869. Mieschner discovered large molecules in the nucleus of the cell that were acidic . He called them nucleic acids. He didn’t know what they were for. Frederick Griffith 1928. 8 0 years later - PowerPoint PPT Presentation

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Page 1: History of The discovery of DNA

History of The discovery of DNA

Page 2: History of The discovery of DNA

Johann Friedrich Mieschner1869

Mieschner discovered large molecules in the nucleus of the cell that were acidic . He called them nucleic acids.He didn’t know what they were for.

Page 3: History of The discovery of DNA

Frederick Griffith1928

• 80 years later• Bacteria could share “genetic

material”.• It could transfer from 1

bacteria to another

Page 4: History of The discovery of DNA

Griffith’s Experiment

Page 5: History of The discovery of DNA

Frederick Griffith’s experiment

• There were 2 kinds of Pneumonococcus bacteria• Rough strain was harmless to the mice.• Smooth strain killed the mice.• If he heat killed the smooth strain then the mice lived.• If he mixed the heat killed smooth bacteria with the

rough strain, then the mice died. • Something was transferred from the dead bacteria

into the live innocuous bacteria that made it deadly. .

Page 6: History of The discovery of DNA

Oswald Avery and coworkers Colin McCleod and Maclyn McCarty1944

• Common belief was protein carried the genetic information.

• Avery removed all the protein from the bacteria and repeated the Griffith experiment. It still transformed the Bacteria

• DNA was the “something” that carried the genetic information

Page 7: History of The discovery of DNA

Linus Pauling1950

• Protein chains were helical. The first twist is called the alpha helix.

• The 2nd twist is the beta sheets• DNA was similar also helical.• He won 2 Nobel prizes 1 in

chemistry for protein structure.

• Nobel peace prize for his work vs. above ground nuclear testing.

Page 8: History of The discovery of DNA

Rosalind Franklin1951

• She perfected the technique of x-ray chrystalography

• Took the first photographs of DNA

• Identified 2 kinds• Her unpublished papers

inspired and supported Watson and Crick.

• Personality clashes with her collegue Wilkins, prevented her from getting credit.

Page 10: History of The discovery of DNA

James Watson and Francis Crick1953• Discovered the double helix

structure of DNA.• Twisted ladder (Left handed twist)• Sugar phosphates sides (anti

parallel)• Nitrogen bases for rungs

(Complimentary)• As you can see they stood on the

support of their collegues.• Won the Nobel Prize 1962 with

Maurice Wilkins. Rosalind Franklin was not included

Page 11: History of The discovery of DNA

Matthew Messelson and Franklin W. Stahl

1958 • Determined the method by which DNA replicated.

• If it was the “Stuff of inhertance” it had to duplicate.

• One new strand and one old strand (Semi conservative)

Page 12: History of The discovery of DNA

Crick and coworkers1961

• The triplicate code• Three DNA nucleotides code for 1 amino acid

Nirenberg and coworkers1964

• Supported Crick’s hypothesis

Page 13: History of The discovery of DNA

Human Genome Project2003• identify all the approximately 20,000-

25,000 genes in human DNA, • determine the sequences of the 3 billion

chemical base pairs that make up human DNA,

• 1993 NIH & Dept of Energy joined to become the National Human Genome Research Institute (NHGRI) Headed by Francis Collins.

• 1998 Craig Venter and Celera Genomics wanted to do it privately and get patents for the genes.

• This was deemed unethical in 2000 but the competition speeded up the process