In the XX-XY system of sex determination, the male is: MCQ with Answer and Explanation

Explanation:
Fertilization in humans typically occurs in the fallopian tube (ampullary region), not the uterus; the zygote then travels to the uterus for implantation. The placenta is the vital organ providing oxygen and nutrients to the growing fetus and removing waste. Spermatogenesis, the production of sperm, occurs in the seminiferous tubules of the testes. Thus, statements 2 and 3 are correct.

Explanation:
Polymerase Chain Reaction (PCR) is a powerful molecular technique used to exponentially amplify a specific segment of DNA, creating millions of copies from a small initial sample. Gel electrophoresis is a laboratory method used to separate DNA, RNA, or protein molecules based on their size and charge by applying an electric field through a gel matrix. Restriction enzymes are molecular scissors that cut DNA at specific sequences; DNA ligase is the enzyme that joins DNA fragments together. Thus, statements 1 and 2 are correct.

Explanation:
The sinoatrial (SA) node, located in the right atrium, generates electrical impulses spontaneously and initiates each heartbeat, setting the rhythm. It is called the natural pacemaker. The atrioventricular (AV) node delays the impulse before it travels to the ventricles. The bundle of His and Purkinje fibers conduct the impulse through the ventricles.