Assertion (A): Gymnosperms do not produce fruits. Reason (R): Their seeds are not enclosed within an ovary. MCQ with Answer and Explanation

Explanation:
After ovulation, the ruptured Graafian follicle transforms into a temporary endocrine structure called the corpus luteum. Its primary function is to secrete large amounts of progesterone (and some estrogen). Progesterone is crucial for maintaining the thickened, highly vascularized uterine endometrium (secretory phase), making it receptive for the implantation of a blastocyst. If fertilization does not occur, the corpus luteum degenerates, progesterone levels drop, and menstruation begins.

Explanation:
Sickle cell anemia is an autosomal recessive disorder caused by a single nucleotide substitution (GAG → GTG) in the β-globin gene, resulting in glutamic acid replaced by valine, producing abnormal hemoglobin S. Under low oxygen, HbS polymerizes, distorting RBCs into sickle shape, causing pain and organ damage.

Explanation:
Salivary amylase (ptyalin) initiates starch digestion in the mouth, hydrolyzing it into maltose and dextrins. Pepsin digests protein, lipase fats, rennin curdles milk. Amylase works optimally at neutral pH.