Which mineral is an essential component of hemoglobin? MCQ with Answer and Explanation

Explanation:
The Operon model, specifically the lac operon model, was proposed by French scientists François Jacob and Jacques Monod in 1961 to explain the regulation of gene expression in prokaryotes (bacteria). They proposed that genes are organized into functional units called operons, consisting of a promoter, an operator, and structural genes, controlled by a regulatory gene. They were awarded the Nobel Prize in Physiology or Medicine in 1965 for this discovery. Beadle and Tatum proposed the 'one gene-one enzyme' hypothesis.

Explanation:
The Loop of Henle is a U-shaped tube extending into the renal medulla. Its primary function is to concentrate the urine by creating a hyperosmotic gradient in the medullary interstitium through the counter-current multiplier mechanism. The descending limb is permeable to water but not salts, while the ascending limb is impermeable to water but actively transports salts out. This gradient allows the collecting duct to reabsorb water under the influence of ADH.

Explanation:
Bacille Calmette-Guérin (BCG) is a live attenuated vaccine against tuberculosis. It is given at birth in many countries. Oral polio vaccine (OPV) for polio.