Assertion (A): The blood-brain barrier protects the brain. Reason (R): It is formed by tight junctions between endothelial cells of brain capillaries. MCQ with Answer and Explanation

Explanation:
Polymerase chain reaction (PCR) uses Taq polymerase, primers, and thermal cycling to make millions of copies of a specific DNA sequence. Southern blotting detects DNA, electrophoresis separates, sequencing reads bases.

Explanation:
The spleen filters blood, removing aged or damaged RBCs, recycles iron, and stores platelets. The liver also processes hemoglobin products, but the spleen is the primary organ for RBC removal. The kidneys filter blood but don't remove RBCs.

Explanation:
Mammalia is the only class of animals that possess mammary glands, which produce milk to nourish their young ones. Other defining features of mammals include the presence of hair on the skin, external pinnae (ear flaps), a four-chambered heart, and being warm-blooded (homeothermic). Examples include humans, whales, and bats.