Download Griffith`s Experiment

DNA: The Genetic Material
Key Experiment (Griffith, 1928)
mice + pneumonia-causing bacteria (SA) = dead mice
mice + dead pneumonia-causing bacteria (SD) = live mice
mice + another type of bacteria (R) = live mice
(Note: R was similar to SA but not deadly.)
mice + R + SD = dead mice + SA (found inside mice)
How did this occur?
Conclusion:
Bacteria R obtained the DNA from the dead pneumoniacausing bacteria (SD).
The R bacteria were changed (or, “transformed”) into SA
bacteria which killed the mice (pneumonia).
The transformed bacteria were able to transmit the
virulent property to offspring.
DNA is the code that determines an organism’s traits.
transformation: The ability of a bacteria to absorb DNA
(transfer genes) from its surroundings.