Question

Two plants are grown. One is engineered to express green fluorescent protein and the other to express firefly luciferase. Which plant will glow in the dark?

• A. Both plants will glow
• B. Neither plant will glow
• C. Plant expressing green fluorescent protein will glow
• D. Plant expressing firefly luciferase will glow

Hint:

One protein needs external light to be seen, the other makes its own light by a chemical reaction.

Answer 1

The Correct Option is D

Step 1: Distinguish fluorescence from bioluminescence. Green fluorescent protein (GFP) is fluorescent, meaning it must first absorb external excitation light (typically blue or UV) and then re-emit green light. It produces no light of its own.
Step 2: Apply this to GFP in darkness. With no excitation source in the dark, GFP cannot fluoresce, so the GFP plant will not glow.
Step 3: Analyze luciferase. Firefly luciferase is a bioluminescent enzyme that oxidizes its substrate luciferin (with ATP, oxygen, and Mg2+) and emits visible light as a chemical reaction product, requiring no incoming light.
Step 4: Apply this to darkness. Because the light comes from the reaction itself, the luciferase plant (when supplied with luciferin) emits light even in complete darkness.
Conclusion: Only the firefly luciferase plant glows in the dark, so the correct answer is option 4.