Scientists wanted to learn more about Griffith’s experiment. They extracted a mixture of various molecules from the heat-killed bacteria. They found that transformation
no longer occurred when they treated the mixture with enzymes that destroyed
DNA
. This experiment supports the hypothesis that
RNA
is the genetic material.

Griffith concluded that the heat-killed bacteria somehow converted live avirulent cells to virulent cells, and he called the component of the dead S-type bacteria the “transforming principle.” Fig. 1.1. Schematic diagram of Griffith's experiment which demonstrates bacterial transformation.

b tumor cells have a cell wall instead of a membrane

explanation:

tumor cells different from normal cells because tumor cells have a cell wall instead of a membrane.