Human parathyroid hormone can be produced in bacterial cells by recombinant DNA technology - Scottish Highers Biology - Question 15 - 2022

To determine in which Petri dish the human parathyroid hormone would be produced, we need to consider how the plasmid and the introduced gene affect bacterial growth in the presence of antibiotics.

1. Understanding the modified plasmid: The modified plasmid contains the human parathyroid hormone gene, which results in the expression of this hormone. The original antibiotic Y resistance gene has been disrupted.

2. Analyzing the media:

   • Petri Dish 1: Contains antibiotic X only. The bacteria with the modified plasmid will grow because they have not lost resistance to antibiotic X. Therefore, they will produce human parathyroid hormone here.
   • Petri Dish 2: Contains antibiotic Y only. Since the modified plasmid lacks the resistance gene for antibiotic Y, the bacteria will not survive in this medium. Thus, no hormone will be produced.
   • Petri Dish 3: Contains both antibiotics X and Y. The bacteria can survive due to resistance to antibiotic X, but cannot survive the presence of antibiotic Y. Therefore, no hormone will be produced in this dish either.

Based on this analysis, the human parathyroid hormone will be produced only in Petri Dish 1.