a. A chemical derived from dead bacteria can produce heritable changes in the traits of living cells.
Explanation:
In 1928 Griffith conducted an experiment with two strains of bacteria <em>Streptococcus pneumoniae</em>, II-R and III-S. III-S was a virulent strain which killed the mice on injecting with it while II-R strain was non virulent and did not harm the mice. When heat killed III-S strain was injected into mice,they again survived because the bacteria were dead.
Griffith then injected heat killed III-S and live II-R strain into the mice. To his surprise, the mice died. He then concluded that living cells of non virulent II-R strain had inherited a chemical from heat killed virulent III-S strain and thus were able to kill the mice. This chemical was called as transforming principle and later was discovered to be DNA. Non virulent strain had been transformed into virulent strain by taking up the DNA from the latter.
