The '9+2' arrangement of microtubules is characteristic of: MCQ with Answer and Explanation

Explanation:
In 1953, Stanley Miller and Harold Urey conducted an experiment to test the Oparin-Haldane hypothesis of chemical evolution. They simulated the reducing atmosphere of primitive Earth, which they believed lacked free oxygen. The gas mixture used was methane (CH4), ammonia (NH3), hydrogen (H2), and water vapor (H2O). By applying electrical sparks (simulating lightning), they successfully synthesized amino acids and other organic compounds.

Explanation:
Scurvy is caused by a deficiency of Vitamin C (Ascorbic acid). Vitamin C is essential for the synthesis of collagen, a structural protein in connective tissues. Its deficiency leads to weakened blood vessels, causing symptoms like bleeding gums, loose teeth, joint pain, and poor wound healing. It was historically common among sailors lacking fresh fruits and vegetables.

Explanation:
Meiosis is reductional division occurring in germ cells to produce haploid gametes (n) from a diploid cell (2n). It involves two successive divisions (Meiosis I and II) and introduces genetic variation through crossing over and independent assortment. Mitosis maintains chromosome number, amitosis is direct division, and fission is asexual reproduction in prokaryotes.