Consider statements about cell division: 1. Mitosis results in four daughter cells. 2. Meiosis involves two successive divisions. 3. Crossing over occurs in mitosis. Which are correct? MCQ with Answer and Explanation

Explanation:
Edward Jenner, an English physician, is known as the 'father of immunology'. In 1796, he developed the world's first successful vaccine against smallpox. He observed that milkmaids who had contracted cowpox (a mild disease) were immune to smallpox. He inoculated a boy with material from a cowpox blister, successfully conferring immunity to smallpox, thus pioneering the concept of vaccination.

Explanation:
Rheumatoid arthritis is an autoimmune disease where the immune system attacks the synovial membranes of joints, causing inflammation and joint damage. Tetanus is bacterial (Clostridium tetani), typhoid is bacterial (Salmonella typhi), malaria is protozoan (Plasmodium). Autoimmune diseases result from failure of self-recognition by immune cells. Other examples: type 1 diabetes, multiple sclerosis, lupus.

Explanation:
Typhoid fever is caused by Salmonella typhi, transmitted through contaminated food and water. Widal test is used for diagnosis. Cholera is Vibrio cholerae.