Consider statements about biotechnology: 1. Agrobacterium tumefaciens is a natural plant genetic engineer. 2. Bt toxin is active in the acidic gut of insects. 3. RNAi is used to silence specific genes. Which are correct? MCQ with Answer and Explanation

Explanation:
The Krebs cycle, also known as the citric acid cycle or TCA cycle, is the central metabolic pathway for the oxidation of acetyl-CoA to produce energy (ATP, NADH, FADH2). It was discovered by the British-German biochemist Sir Hans Adolf Krebs in 1937. He was awarded the Nobel Prize in Physiology or Medicine in 1953 for this discovery. Melvin Calvin elucidated the carbon pathway in photosynthesis.

Explanation:
DNA ligase seals the phosphodiester bonds between adjacent DNA fragments, joining them together. In recombinant DNA technology, it is used to ligate the gene of interest into a vector. Restriction enzymes cut DNA, DNA polymerase synthesizes DNA, and helicase unwinds the double helix. Ligase is essential for finalizing the recombinant DNA molecule.

Explanation:
Essential amino acids (like lysine, tryptophan) cannot be synthesized by the human body and must be obtained through the diet. Dietary fiber (roughage) is indigestible plant material that adds bulk to stool, promotes peristalsis, and aids in digestion and preventing constipation. Saturated fats have no double bonds between carbon atoms, making them solid at room temperature (like butter); unsaturated fats are liquid (like oils). Thus, statements 1 and 3 are correct.