Final answer:
Oswald Avery, Colin MacLeod, and Miclyn McCarty first demonstrated that DNA is the transforming principle in cells, leading to permanent changes in new cells. Their experiments in 1944 showed that purified DNA from heat-killed S strain bacteria could transform R strain bacteria into a virulent form.
Step-by-step explanation:
Identification of the Transforming Principle
The scientist or team of scientists who first demonstrated that cells contain some component that can be transferred to a new population of cells and permanently causes changes in the new cells were Oswald Avery, Colin MacLeod, and Miclyn McCarty. In 1944, following up on the groundwork laid by Frederick Griffith's transformation experiments, they conducted a series of experiments which provided evidence that DNA was the transforming principle that could cause inheritable changes in cells. They accomplished this by using purified components from heat-killed S strain Streptococcus pneumoniae and demonstrating that only the DNA fraction was able to transform non-virulent R strain bacteria into virulent S strain bacteria. This was a pivotal moment in biology, as it shifted the scientific consensus away from proteins and toward DNA as the carrier of genetic information.
Although initially the scientific community was reluctant to accept that DNA was the genetic material, due to its perceived simplicity, additional proof came in the form of experiments by Martha Chase and Alfred Hershey in 1952, which confirmed that DNA, and not protein, was the genetic material. However, the scientists first demonstrated the transforming ability of DNA were indeed Avery, MacLeod, and McCarty, although they unfortunately did not receive the Nobel Prize for this groundbreaking discovery.