Final answer:
If proteases had prevented transformation in the Avery, MacLeod, and McCarty experiments, scientists would have concluded that proteins are the genetic material.
Step-by-step explanation:
In the experiments performed by Avery, MacLeod, and McCarty, if the use of proteases (enzymes that break down proteins) had prevented the transformation of R strain bacteria, the scientists would have concluded that proteins are the genetic material. This is because these experiments were designed to determine which substance was responsible for transferring genetic information during the process known as transformation.
Since it was actually found in their experiments that only when DNA was destroyed was the transformation effect lost, DNA was concluded to be the genetic material. However, if proteases had stopped the transformation, it would imply that proteins carried the genetic information necessary for transformation.