Question

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?

• dna passed from the heat - killed strain to the living strain.
• protein passed from the heat - killed strain to the living strain.
• the phosphorescence in the living strain is especially bright.
• descendants of the living cells are also phosphorescent.

Explanation:

A heritable trait is one that can be passed from parent to offspring. To show phosphorescence is heritable, we need to see if the offspring of the now - phosphorescent living cells also have the trait.

• For the option "DNA passed from the heat - killed strain to the living strain": Just knowing DNA is passed doesn't directly show the trait is heritable. Heritability is about the trait being passed to offspring, not just the transfer of DNA.
• For the option "Protein passed from the heat - killed strain to the living strain": Proteins don't carry heritable information in the same way as DNA for traits, and this doesn't show the trait is passed to offspring.
• For the option "The phosphorescence in the living strain is especially bright": The brightness of phosphorescence has nothing to do with whether the trait is heritable.
• For the option "Descendants of the living cells are also phosphorescent": If the descendants (offspring) of the living cells that became phosphorescent are also phosphorescent, this shows that the ability to phosphoresce was passed from the parent (the now - phosphorescent living cell) to the offspring, which is the definition of a heritable trait.

Answer:

D. Descendants of the living cells are also phosphorescent.