What is the purpose of inserting the spider gene into a plasmid that also contains the EGFP marker gene?

• A. To enable identification of transformed individuals by fluorescence and to express the spider gene in silk glands
• B. To ensure expression in all tissues
• C. To silent the spider gene in non-silk tissues
• D. To increase plasmid copy number

Answer: (A)

The idea here is to use a visible marker alongside the gene of interest so you can both identify which cells have taken up the plasmid and drive the desired protein in a specific tissue. EGFP serves as a reporter that glows under appropriate light, so transformed individuals or cells can be identified simply by their fluorescence. At the same time, the plasmid is designed to express the spider gene in silk glands, usually by a promoter that targets that tissue. This pairing lets researchers select transformants via fluorescence and ensure the spider silk protein is produced where it’s needed.

Why the other ideas don’t fit: expressing in all tissues would require a universal promoter, which isn’t implied by just having the EGFP marker and spider gene in the plasmid. silencing the spider gene in non-silk tissues isn’t the stated aim and would need additional regulatory elements to repress expression elsewhere. increasing plasmid copy number is about replication control and not about using a fluorescent marker to identify transformants or target expression to a specific tissue.