DNA History/Structure

What was Frederick Griffith’s experiment?

Griffith injected two strands of strep, 4 different ways into mice. 1. S (virulent with a protective polysaccharide capsule) strand led to death. 2. R (non virulent and lacking a protective capsule) strand the mice did not get sick. 3. Heat killed S strain, mice stay healthy. 4. Mixture of heat killed S and live R, mice got sick and died.

What was Griffith’s conclusion

Something from the heat killed S bacteria got into the live R strain of bacteria and transformed them to virulent S bacteria.

What was JL Alloway’s experiement

Alloway did the same experiemnt as Griffith without the mice. He used test tubes with R and S strands and let them incubate. He found only S strand bacteria in the test tube.

What was JL Alloway’s conlcusion

Live R bacteria somehow obtained genetic material from dead S bacteria.

What was Avery, Macleod and McCarty’s experiement?

They incubated DNA extracted from heat killed S bacteria with live R bacteria. They found that all the bacteria turned into live S bacteria.