Located throughout the body, veins return deoxygenated blood to the heart. Veins have valves to prevent backflow of blood and larger lumens (internal spaces) than arteries. The vein lumen has a smooth endothelium, or inner lining. The endothelium is part of the tunica intima, the innermost layer of the vein wall
Restriction enzymes are DNA cutting enzymes found within bacteria. They can cut the DNA molecule.
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