DNA- The genetic material

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DNA- The genetic material

• History

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Some of the Important Scientists in Biotechnology

• Griffith
• Avery et. al.
• Hershey and Chase
• Rosalind Franklin
• Watson, Crick and Wilkins

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Griffith's Experiment
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• 1944
• Oswald Avery, Colin MacLeod and Maclyn McCarty
  prove that DNA carries genetic information.

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• Phage reproductive cycle

Phage attaches to bacterial cell.
Phage injects DNA.
Phage DNA directs host cell to make more phage
DNA and protein parts. New phages assemble.
Cell lyses and releases new phages.
Figure 10.1C
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• The Hershey-Chase Experiment

Agitate in a blender to separate phages outside
the bacteria from the cells and their contents.
Centrifuge the mixture so bacteria form a pellet
at the bottom of the test tube.
Measure the radioactivity in the pellet and
liquid.
Mix radioactivelylabeled phages with bacteria.
The phages infect the bacterial cells.
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Radioactiveprotein
Emptyprotein shell
Radioactivityin liquid
Phage
Bacterium
PhageDNA
DNA
Batch 1Radioactiveprotein
Centrifuge
Pellet
RadioactiveDNA
Batch 2RadioactiveDNA
Centrifuge
Radioactivityin pellet
Pellet
Figure 10.1B
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• The Hershey-Chase experiment showed that certain
  viruses reprogram host cells to produce more
  viruses by injecting their DNA

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• James Watson and Francis Crick worked out the
  three-dimensional structure of DNA, based on work
  by Rosalind Franklin

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Roslind Franklin assisted in the discovery, but
died before the Nobel Prizes were awarded.
1953

• James Watson and Francis Crick
• describe the double helical structure of DNA.
  They shared the 1962 Nobel Prize in Medicine or
  Physiology with Maurice Wilkins.