1st major experiment on genetic material,Fredick Griffith (1928)
Question 1: How do bacteria cause pne


  • Only 1 strain caused pneumonia .
  • Smooth edged colonies caused pneumonia.
  • Rough edged colonies did not cause pneumonia
  • Mice injected with smooth edged bacteria died ,those injected with rough edged bacteria lived (surprise, surprise!)
Question 2; Did the smooth edged bacteria secrete a deadly toxin ?
  • Experiment :Griffith heat killed some smooth bacteria & then injected it into the mice.The mice lived.
Then Griffith mixed some heat-killed smooth bacteria with living rough bacteria.Since both of these are harmless on thier own, you might exspect the mice to live.
  • Experiment (cont)
- -But they died
-Conclusion:somehow the disease causing bacteria passed on a gene to the non-disease causing bacteria.
-This process is called transformation.
  • some genetic factor was bein transformed from the heat -killed smooth bacteria to the living rough bacteria
  • Q:watz da genetic material made of?
  • answered by Oswald Avey in 1944.
  • Avery wrked to determine wat molecule the genetic material was
  • experiment 1;Avery made an extract from