Consider statements about human nutrition: 1. Calcium is essential for blood clotting. 2. Iron is a component of hemoglobin. 3. Iodine is required for thyroid hormone synthesis. Which are correct? MCQ with Answer and Explanation

Explanation:
Growth hormone (somatotropin) stimulates protein synthesis, cell division, and growth of bones and muscles, especially during childhood. Thyroxine regulates metabolism, cortisol is a stress hormone from the adrenal cortex, adrenaline is from the adrenal medulla. GH deficiency leads to dwarfism; excess causes gigantism or acromegaly.

Explanation:
Cyanobacteria (blue-green algae) are photosynthetic, oxygenic prokaryotes that play a crucial role in nitrogen fixation in aquatic and terrestrial ecosystems. Mycorrhiza is a mutualistic symbiotic association between a fungus and the roots of a vascular plant, where the fungus aids in nutrient absorption and the plant provides carbohydrates. Nitrosomonas is a nitrifying bacterium that converts ammonia to nitrite; denitrifying bacteria like Pseudomonas convert nitrates to nitrogen gas. Thus, statements 1 and 2 are correct.

Explanation:
The Central Dogma of molecular biology was proposed by Francis Crick in 1958. It describes the fundamental flow of genetic information within a biological system: DNA is transcribed into RNA, and RNA is translated into protein. The flow is typically unidirectional: DNA -> RNA -> Protein. While exceptions exist (like reverse transcription in retroviruses, where RNA -> DNA), the central dogma remains the core principle of gene expression.