Transcript History of DNA-Discovery and Structure

History of DNA-Discovery
and Structure
Feb. 20, 2009
Frederick Griffith
• 1928
• British
• Isolated two slightly different strains of
pneumonia bacteria from mice,
experimented, and discovered
transfomation.
Griffith- Experiment
Griffith-Experiment
• What does this mean?
– Transformation of non-deadly strain by heatkilled deadly strain.
– This told Griffith that some type of
information could be passed between two
different strains.
– Hypothesized that genes were passed.
Beadle and Tatum
• 1941
• Used radiation and bread mold to
investigate enzymes (proteins).
• Determined the “one gene, one enzyme”
relationship.
Beadle and Tatum-Experiment
Beadle and Tatum-Experiment
• What does this mean?
– By changing a single gene in the mold, a
single enzyme was changed.
– Each gene codes for an enzyme- one gene,
one enzyme.
Avery
• 1944
• Canadian
• Repeated Griffith’s work.
• Wanted to know what molecule was being
transferred to cause the transformation.
• Discovered that DNA stores and carries
genetic information from one generation
to another.
• No one believed him.
Avery-Experiment
Griffith
Avery
Avery-Experiment
• What does this mean?
– When proteins in the deadly strain were
destroyed the cell could still transform the
non-deadly strain mouse died, not protein
passing genetic information.
– When DNA in the deadly strain was
destroyed the cell could not transform the
non-deadly strain mouse lives, DNA passes
genetic information.
Hershey and Chase
• 1952
• American
• Used radioactive bacteriophages (virus
that kill bacteria) to determine what
molecule was carrying the genetic
material.
• Determined that the genetic material in
the bacteriophage was DNA, not protein.
Hershey-Chase-Experiment
Hershey-Chase-Experiment
• What does this mean?
– When protein was followed from the virus to
the bacteria, it stayed with the virus not
being passed on as genetic material.
– When DNA was followed from the virus to
the bacteria, it ended up in the bacteria
passed on as genetic material.
– It is DNA that contains the genetic code.
Homework-Due Feb. 23!
• Create a timeline showing when Mendel,
Griffith, Beadle, Tatum, Avery, Hershey, and
Chase worked.
• Include a brief description of each experiment
and what the experiment proved.
• Include at least two pictures/diagrams.
• The timeline should be at least the length of two
pieces of paper (about 22 inches).
• Any extra effort will be rewarded.