Consider statements about plant reproduction: 1. Pollination is the transfer of pollen to the stigma. 2. Double fertilization is unique to gymnosperms. 3. Seeds develop from ovules. Which are correct? MCQ with Answer and Explanation

Explanation:
Zymase is the enzyme complex in yeast that catalyzes alcoholic fermentation, converting pyruvate to ethanol and CO₂. Invertase hydrolyzes sucrose, lactase breaks lactose, maltase breaks maltose. Zymase activity is exploited in baking and brewing industries.

Explanation:
Mutations are random changes in DNA sequence that create new alleles, serving as the ultimate source of genetic variation. Natural selection, genetic drift, and gene flow act on existing variation but do not create new alleles. Mutations can be beneficial, neutral, or deleterious, and are essential for evolution.

Explanation:
The lac operon in E. coli is a classic example of an inducible operon. It is normally 'off' (repressed) because the lac repressor protein, produced by the 'i' gene, binds to the operator, preventing transcription of the structural genes (z, y, a) needed for lactose metabolism. However, when lactose is present in the environment, it is converted to allolactose, which acts as an inducer. Allolactose binds to the repressor, changing its shape and preventing it from binding to the operator, thus 'inducing' or allowing transcription to occur.