Explain why a marker gene (EGFP) was used along with the spider gene in the plasmid.

• A. The marker gene glows under UV to indicate uptake of the plasmid
• B. The marker gene increases silk production
• C. The marker gene prevents degradation
• D. The marker gene ensures expression only in silk glands

Answer: (A)

The main idea is to have a visible reporter that shows whether the plasmid is present and active. EGFP encodes a fluorescent protein, so cells that have taken up the plasmid and are expressing the construct will glow green under UV/blue light. This lets researchers quickly confirm delivery and expression without guessing, which is essential before attempting to study the spider gene’s product. The fluorescent marker doesn’t itself boost silk production, prevent degradation, or dictate where the gene is expressed—that relies on the promoter and other regulatory elements—so the marker’s job is simply to indicate successful uptake and expression of the plasmid.