The jellyfish gene attached to the human Factor IX gene codes for a protein that glows green under fluorescent light. What is this protein called?

• A. Hemoglobin
• B. Insulin
• C. Green fluorescent protein
• D. Luciferase

Answer: (C)

The main idea here is using a fluorescent reporter to visualize gene expression. Green fluorescent protein is the protein that naturally emits green light when illuminated with blue light, making it a powerful marker to track where and when a gene is active. Since the jellyfish GFP gene has been attached to the human Factor IX gene, the resulting protein product can be seen as green under fluorescence, indicating expression of that gene.

Hemoglobin and insulin are not fluorescent markers; they don’t glow under fluorescent light. Luciferase can produce light, but it does so through a chemical reaction (bioluminescence) and isn’t the same kind of green fluorescence produced by GFP. Green fluorescent protein is the classic, direct fluorescent marker, which is why it’s the correct choice.