4 Smooth Strain ! Mice were injected with the live S strain. ! All of the mice developed pneumonia and died Rough Strain ! Mice injected with a sample of the Rough strain of bacteria did not get pneumonia and lived. Heat-killed Smooth Strain ! Smooth strain is heated until cells die. ! Mice injected with test sample did not get pneumonia and lived. The Transforming Factor ! Griffith combined the live R strain and heat-killed S strain. ! Mice injected with the mixture contracted pneumonia and died. ! Griffith proposed the presence of a factor within dead cells that can be used to Transform live cells.
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Smooth Strain Rough Strain - Nassau Community College
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4
Smooth Strain
! Mice were injected with the live S strain.
! All of the mice developed pneumonia and died
Rough Strain
!Mice injected with a sample of the Roughstrain of bacteria did not get pneumoniaand lived.
Heat-killed Smooth Strain
! Smooth strain is heated until cells die.
! Mice injected with test sample did not get pneumonia
and lived.
The Transforming Factor
! Griffith combined the live R
strain and heat-killed S
strain.
! Mice injected with the
mixture contracted
pneumonia and died.
! Griffith proposed the
presence of a factor within
dead cells that can be used
to Transform live cells.
5
Transformation revisited
Why do it again?
rediscovered!!!!!
1944
Avery, McCarty & MacLeod
! Worked at Cold Spring Harbor, Long Island. Facility
was built by the US Army
! They continued Griffith’s work -
Using Enzyme Extracts.! Used enzymes to digest away selected components