Active Log Phase & Biomass Production — NEET Biology

Correct answer: C — S4 and S5 are not correct

Let's evaluate each statement regarding recombinant protein production: S1 is correct: The first fundamental step in genetic engineering is the identification and isolation of the desired gene from the source organism. S2 is correct: Transformation is the established procedure for introducing a foreign piece of DNA into a host bacterium. S3 is correct: Bioreactors are designed for large-scale culturing (typically 100-1000 litres) to provide optimal conditions (temperature, pH, oxygen, etc.) for high yield of the desired product. S4 is not correct: Gram staining is a differential staining technique used for classifying bacteria based on their cell wall characteristics, not for selecting host cells that have taken up recombinant DNA. Selectable markers (e.g., antibiotic resistance genes) are used for this purpose. S5 is not correct: Downstream processing, which includes separation and purification, is performed *after* the biosynthetic stage (i.e., after the product has been formed in the culture), not prior to it. S6 is correct: Bioprocess engineering focuses on maintaining sterile (contamination-free) conditions to ensure the exclusive growth of the desired organism for biotechnological product manufacture. Therefore, S4 and S5 are the statements that are NOT correct. The core concept tested is the accurate understanding of the various techniques and stages involved in recombinant DNA technology and large-scale protein production.