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why doesnt Dr. Bayul tell you the anwser hes a rock formation guy not you if you dont know the anwser
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Explanation:
The immune system protects the body from possibly harmful substances by recognizing and responding to antigens. Antigens are substances (usually proteins) on the surface of cells, viruses, fungi, or bacteria. Nonliving substances such as toxins, chemicals, drugs, and foreign particles (such as a splinter) can also be antigens. The immune system recognizes and destroys, or tries to destroy, substances that contain antigens.
Your body's cells have proteins that are antigens. These include a group of antigens called HLA antigens. Your immune system learns to see these antigens as normal and usually does not react against them.
The DNA has to replicate during the S phase so that each new cell that is forming can get it's own replica of the original cell's DNA molecule
