Consider statements about diseases: 1. Cholera is caused by a bacterium. 2. AIDS is caused by a retrovirus. 3. Dengue is transmitted by Culex mosquito. Which are correct? MCQ with Answer and Explanation

Explanation:
Polymerase Chain Reaction (PCR) is a powerful molecular technique used to exponentially amplify a specific segment of DNA, creating millions of copies from a small initial sample. Gel electrophoresis is a laboratory method used to separate DNA, RNA, or protein molecules based on their size and charge by applying an electric field through a gel matrix. Restriction enzymes are molecular scissors that cut DNA at specific sequences; DNA ligase is the enzyme that joins DNA fragments together. Thus, statements 1 and 2 are correct.

Explanation:
During photosynthesis, water is split (photolysis), releasing oxygen as a byproduct. Respiration consumes oxygen, nitrogen fixation uses nitrogenase, transpiration releases water vapor.

Explanation:
Cristae are the numerous infoldings of the inner mitochondrial membrane that increase surface area for oxidative phosphorylation and ATP synthesis. They contain ATP synthase complexes. Thylakoids are membrane structures in chloroplasts; grana are stacks of thylakoids. Cisternae are flattened membrane sacs of ER and Golgi. Cristae give the inner membrane its characteristic folded appearance.