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Copy of 12.1 Identifying the Substance of Genes

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Jonathan Brown

on 18 February 2014

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Transcript of Copy of 12.1 Identifying the Substance of Genes

Injecting Mice Simulation
Why did the last mouse die???
Both the heat-killed S cells and the R cells by themselves were harmless but when they were mixed together they killed the mouse.

Griffith concluded that the heat killed- S cells must have passed their disease-causing ability to the R cells.
S strain vs. R strain
The "S" stands for SMOOTH


The S strain colonies caused pneumonia

Think: S Sick

Transformation
Griffith called this process transformation because one type of bacteria (harmless) had been changed or "transformed" into another type (harmful).
Avery's Discovery
In 1944, Oswald Avery and a team of scientists wanted to know which molecule was responsible for transformation that Griffith observed in his experiments.

Avery found out that when DNA was broken down in the heat killed-S cells, transformation would NOT occur.


12.1 Identifying the Substance of Genes
Frederick Griffith
In 1928, Griffith was trying to figure out how a certain type of bacteria gave people pneumonia.

He isolated two very similar types of the same bacterial species.

One caused pneumonia, one did not
The "R" stands for ROUGH


The R strain colonies DID NOT cause pneumonia

http://www.quia.com/files/quia/users/hlrbiology/Animations/08_DNA_and_Proteins/Griffith_Mouse_Experiment.swf
Make predictions on your guided notes!!!

Avery concluded that the nucleic acid
DNA
stores and transmits genetic information from one generation of bacteria to the next!
Hershey-Chase Experiment
In 1952, Alfred Hershey and Martha Chase studied
bacteriophages
in order to determine whether it was DNA or protein that was the genetic material.

Bacteriophage
= a type of virus that infects a bacterial cell or
bacterium.

Hershey-Chase Experiment
Hershey and Chase used radioactive markers to "label" DNA and protein in the bacteriophage.

Phosphorus-32 for DNA

Sulfur-35 for protein
Hershey and Chase's experiment with bacteriophages confirmed Avery's results, convincing many scientists that
DNA
was the genetic material found in all living things.
Full transcript