Why was it important that the spider gene was expressed only in the silk glands of the silkworms?

• A. So that the spider protein can be harvested from silk and to avoid potential harm in other tissues
• B. To ensure expression in all tissues
• C. To accelerate embryo development
• D. To prevent any expression in silk glands

Answer: (A)

The key idea is tissue-specific expression: you want the spider gene active only in the silk glands so the spider silk protein is produced where it can be harvested and not in other parts of the organism. Silk glands are specialized secretory tissues that routinely manufacture and secrete large silk proteins into the silk fiber, so putting the spider gene there means the protein is made directly into the silk cocoons. This makes collection practical while reducing risks to the rest of the silkworm, since expressing spider protein in other tissues could disrupt normal biology or harm the animal. That’s why limiting expression to the silk glands is the best approach. Expressing in all tissues would be wasteful and potentially harmful, and the goal isn’t to accelerate development or to prevent expression in silk glands.