Oswald Avery, Colin Mcleod, and Maclyn McCarty | history of genetics|

 Oswald Avery, Colin Mcleod, and Maclyn McCarty

Oswald Avery, Colin Mcleod, & Maclyn McCarty

 

These three scientists take the work of Griffith step up and discover the mysterious material that was not well explained by Griffith. This mysterious material was DNA that was discovered by Friedrich Miescher in 1869 and recognized by Avery, Mcleod, and McCarty in 1944.

Now, have a look at Griffith’s work then move forward.

• Griffith experimented on mice. 
• He injected S-type and R-type streptococcus pneumonia in mice. 
• Insertion of S-type results in the death of mice while R-type bacteria did not result in the death of mice. 
• Heat-killed S-type is also non-infectious. 
• When he injected both heat-killed S-type and R-type bacteria in mice, the mice were dead.
• He said that something was transformed from a heat-killed S-type to an R-type strain of bacteria but he did not recognize that material.

This mystery was solved by Avery, Mcleod, and McCarty.

They assume that the material moves from heat-killed S-type bacteria to R-type bacteria must be protein, RNA, or DNA.

1. So, they used protease enzyme and they observed that protein-digesting enzyme or protease failed to inhibit the transformation from heat-killed S-type to R-type bacteria.
2. They used RNA digesting enzyme and this time the same result was seen by them as in the case of protease. The RNA digestion was also unable to stop the transformation.
3. They used DNA digesting enzyme and this time they succeeded and the transformation was inhibited.

They concluded from his work that DNA is the material that transformed from heat-killed S-type bacteria to R-type bacteria.

Their experiment also shows that DNA is the genetic material of cells.