Assertion (A): Diabetes mellitus is characterized by hyperglycemia. Reason (R): It is caused by deficiency or resistance to insulin. MCQ with Answer and Explanation

Explanation:
Max Theiler developed the attenuated yellow fever vaccine (17D strain) in the 1930s, winning the Nobel Prize. Pasteur rabies, Jenner smallpox, Salk polio.

Explanation:
In the XX-XY system of sex determination, found in humans and most mammals, females have two identical sex chromosomes (XX) and are homogametic, producing only X-bearing eggs. Males have two different sex chromosomes (XY) and are heterogametic, producing two types of sperm: 50% with X and 50% with Y. The sperm determines the sex of the offspring.

Explanation:
Color blindness (specifically red-green color blindness) is an X-linked recessive disorder. The gene responsible is located on the X chromosome. Males (XY) are more frequently affected because they only have one X chromosome; a single recessive allele will cause the disorder. Females (XX) need two recessive alleles to be affected, making them more likely to be carriers.