Notes from NEET topper
Avery, MacLeod, and McCarty Experiment
Objective:
The primary aim was to identify the macromolecule responsible for genetic transformation in bacteria.
Background:
Building upon Griffith’s transformation experiment, which demonstrated that a substance could transform non-virulent bacteria into virulent ones.
Experimental Process:
Avery, MacLeod, and McCarty isolated cellular components (DNA, RNA, proteins) from the S strain of Streptococcus pneumoniae bacteria and treated it with DNase, RNases and Protease separately.
This cell extract was then mixed with the non-virulent R strain
This extract was injected in mice
Observations:
The experiment revealed that when the cell extract was treated with protease, the virulent S-strain developed. Conversely, when the cell extract was treated with DNase, the virulent S-strain did not develop.
Conclusion
This experiment confirmed that DNA was the transforming principle by using enzymes to selectively degrade DNA, RNA, and proteins in heat-killed bacteria.
Only the destruction of DNA prevented transformation.
