Explain 'Transforming Principle' in Griffith experiment,'S strain and R strain' in griffith experiment?
Transforming Principle
-
Griffith performed experiments with the bacteria Streptococcus pneumoniae. This bacterium has two strains − S strain and R strain.
-
S strain Bacteria
R strain Bacteria
-
Produce smooth colonies on culture plate
-
Produce rough colonies on culture plate
-
Have a polysaccharide coat
-
Do not have a polysaccharide coat
-
Virulent (causes pneumonia)
-
Non-virulent (does not cause pneumonia)
-
-
Griffith’s experiment
-
Live R strain in the presence of heat-killed S strain produce virulence because somehow R strain bacteria is transformed by heat-killed S strain bacteria. Hence, it was concluded that there must be transfer of genetic material.
Biochemical Nature of Transforming Material
-
Avery, McLeod, and McCarthy worked to determine the biochemical nature of genetic material responsible for transformation.
-
This suggests that DNA has to be the genetic material.
R strain of Streptococcus pneumonia is not virulent as it does not produce polysaccharide coat (virulence factor).
S strain of Streptococcus pneumonia is virulent due to the presence of polysaccharide capsule