Psychic stimulants include caffeine, cocaine, and various amphetamines. These drugs are used to enhance mental alertness and reduce drowsiness and fatigue.
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What are so called breast-cancer genes, are mutations in two genes: BRCA1 (BReast CAncer gene one) and BRCA2 (BReast CAncer gene two), and are also associated with ovaric cancer. According to the question, these genes are present in the popolation despite surgeries and deaths, and asks why. Surgeries does not eliminate the genes, they eliminate the tumors, and people can still reproduce after that. And also, most people already had offspring before they know they have cancer, so they are inheriting the mutations on the genes anyway.
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