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A part of the cell containing DNA and RNA and responsible for growth and reproduction
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Any histologically identifiable mass of neural cell bodies in the brain or spinal cord
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The central structure of the lens that is surrounded by the cortex
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A small group of indispensable persons or things
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The positively charged dense center of an atom
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(astronomy) the center of the head of a comet; consists of small solid particles of ice and frozen gas that vaporizes on approaching the sun to form the coma and tail