The phenomenon where a single gene influences multiple, seemingly unrelated phenotypic traits is known as: MCQ with Answer and Explanation

Explanation:
Kala-azar, also known as visceral leishmaniasis, is a severe systemic disease caused by the protozoan parasite Leishmania donovani. The disease is transmitted to humans through the bite of an infected female Phlebotomus sandfly (in the Old World) or Lutzomyia sandfly (in the New World). The sandfly injects the infective promastigote stage of the parasite into the skin during a blood meal. Anopheles transmits malaria, Aedes transmits dengue and yellow fever, and Culex transmits filariasis.

Explanation:
Natural passive immunity is transferred from mother to child via placental transfer of IgG antibodies (in utero) and IgA antibodies in breast milk (colostrum). It provides temporary protection without the infant's immune system being activated. Active immunity results from natural infection or vaccination.

Explanation:
Gastrin is a hormone secreted by G cells in the stomach antrum, stimulating parietal cells to secrete HCl and promoting gastric motility. It is released in response to food in the stomach.