Question

Fred Griffith studied two strains of Streptococcus pneumonia, one that causes a lethal infection when injected into mice, and a second that is harmless. He observed that

pathogenic bacteria that have been killed by heating can no longer cause an infection. But
when these heat-killed bacteria are mixed with live, harmless bacteria, this mixture is capable of infecting and killing a mouse. What did Griffith conclude from this
experiment?
(a) The infectious strain cannot killed by heating.
(b) The heat-killed pathogenic bacteria "transformed" the harmless strain into a lethal one.
(c) The harmless strain somehow revived the heat-killed pathogenic bacteria.
(d) The mice had lost their immunity to infection with S. pneumoniae.

Answer 1

The correct answer is b The heat killed pathogenic bacteria transformed the harmless strain into a lethal one.

Step-by-step explanation:

Griffith used S.pneumoniae to study whether DNA is the genetic material or not.

The heat killed pathogenic bacteria can no longer cause infection.But when these heat killed bacteria are mixed with live harmless bacteria this mixture is capable of infecting and killing a mouse .This incident occurs due to DNA transformation which leads to transfer of DNA from heat killed pathogenic bacteria to the live harmless bacteria thus transforming the harmless bacteria into lethal and infectious agent.