1. Some substance must be responsible for passage of traits from parents to offspring. For a substance to do this it must be:
a. Stable enough to store information for long periods.
b. Able to replicate accurately.
c. Capable of change to allow evolution.
Griffith worked with 2 strains of S. pneumoniae
1st strain had a smooth capsule that protected the bacterium from body’s defense systems (S)
Virulent – (full of poison) able to cause disease
2nd strain lacked capsule and didn’t cause disease (R)
Mice injected with (S) strain died; mice injected with (R) strain lived