Question

Heat killed pathogenic NL cells and live non-pathogenic cells are mixed and injected into mice. The result would be

• A. Mice develop disease and die.
• B. Mice die without developing disease.
• C. Mice remain healthy.
• D. 50% mice develop disease and die.
• E. All mice remain healthy but lose vision.

Answer 1

Answer: (A)

Mice develop disease and die.

Transformation is the transfer of genetic material from one bacterial strain to other without establishing a physical contact. According to the question, heat-killed pathogenic NL cells and live non-pathogenic cells are mixed and injected into mice. It will cause infection and mice will die because a transforming substance/DNA is transferred from heat-killed strain to non-virulent strain causing non-virulent strain to transform into virulent/pathogenic form. This makes option A correct. If mice die without developing the disease; the death is caused by any other factor and there is no role of infection which makes option B incorrect. As DNA from pathogenic strain has transformed the non-pathogenic bacteria into the pathogenic one, mice cannot remain healthy upon infection; this makes options C, D and E incorrect. The correct answer is A.