Answer:
Environmental exposure to certain chemicals, ultraviolet radiation, or other external factors can also cause DNA to change. These external agents of genetic change are called mutagens.
Thymine always pairs with adenine.
The blood-brain barrier functions to regulate the movement of materials from the blood to the brain (option A).
<h3>What is the blood-brain barrier?</h3>
The blood-brain barrier is a structure in the central nervous system (CNS) that keeps various substances found in the bloodstream out of the brain while allowing in the substances essential to metabolic function, e.g. oxygen.
The blood-brain barrier serves as a protective barrier for the brain that prevents the entry of substances in the bloodstream that can cause brain damage.
Therefore, the blood-brain barrier functions to regulate the movement of materials from the blood to the brain.
Learn more about blood-brain barrier at: brainly.com/question/9643165
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