The inheritance of skin color in humans is an example of: MCQ with Answer and Explanation

Explanation:
African sleeping sickness (trypanosomiasis) is caused by Trypanosoma brucei and transmitted by the bite of the tsetse fly (Glossina). Malaria is by mosquito, typhoid by housefly (mechanical), Lyme disease by tick.

Explanation:
In the lac operon, the 'i' gene (regulatory gene) constitutively produces a repressor protein. In the absence of lactose (the inducer), this active repressor binds specifically to the operator region of the operon. The operator overlaps with the promoter, physically blocking RNA polymerase from binding to the promoter or moving forward to transcribe the structural genes (z, y, a). When lactose is present, it binds to the repressor, inactivating it and allowing transcription.

Explanation:
Aspergillus niger is a fungus widely used for the industrial production of citric acid (a common food additive) through fermentation. Penicillium chrysogenum produces penicillin, Saccharomyces cerevisiae is used in baking and brewing, Rhizobium is a nitrogen-fixing bacterium. Citric acid is used as a preservative and flavor enhancer.