Consider statements about vitamins: 1. Vitamin D is synthesized in the skin upon sunlight exposure. 2. Vitamin B12 is the only vitamin containing a metal ion. 3. Vitamin A is essential for blood clotting. Which are correct? MCQ with Answer and Explanation

Explanation:
Totipotency is the genetic ability of a single plant cell to divide and differentiate into all the cell types of the plant, ultimately generating an entire new plant. This property is the fundamental basis of plant tissue culture. Micropropagation is the technique used to rapidly multiply plants using this totipotency, often through the formation of callus and somatic embryos.

Explanation:
The Casparian strip is a waterproof band of suberin and lignin found in the radial and transverse cell walls of the endodermis (the innermost layer of the cortex) in plant roots. It acts as a barrier to the passive flow of water and dissolved minerals through the cell walls (the apoplastic pathway). This forces water and solutes to cross the selectively permeable plasma membrane and enter the symplastic pathway, allowing the plant to control and filter what enters the vascular cylinder (stele).

Explanation:
Lactase is a brush border enzyme of the small intestine that hydrolyzes the disaccharide lactose (milk sugar) into its constituent monosaccharides, glucose and galactose. Maltase acts on maltose, sucrase on sucrose, and amylase on starch. Lactose intolerance results from lactase deficiency, causing gastrointestinal symptoms after dairy consumption.