After mixing a heat-killed, phosphorescent (light-emitting) strain of bacteria with a living, nonphosphorescent strain, you discover that some of the living cells are now phosphorescent. Which observation(s) would provide the best evidence that the ability to phosphoresce is a heritable trait?
A) DNA passed from the heat-killed strain to the living strain.
B) Protein passed from the heat-killed strain to the living strain.
C) The phosphorescence in the living strain is especially bright.
D) Descendants of the living cells are also phosphorescent.
E) Both DNA and protein passed from the heat-killed strain to the living strain.

Question

Quizplus · Accepted Answer

The best evidence that the ability to phosphoresce is a heritable trait is to observe that the descendants of the living cells that acquired the trait are also phosphorescent. This suggests that the genetic information responsible for the trait was passed down from the initial mixing of the two strains, which could only occur through the transfer of DNA. Options A and E suggest the possibility of DNA transfer, but do not provide evidence that the trait is heritable. Option B suggests the transfer of a protein, which alone is not sufficient to suggest that the trait is heritable. Option C is not relevant to heritability, as brightness of the phosphorescence could be affected by many factors besides genetics.

After Mixing a Heat-Killed, Phosphorescent (Light-Emitting) Strain of Bacteria with a Living