Anatomy & Physiology Question #3


The nurse is reviewing the letters A, T, G, and C in the DNA code. If the chemicals adenine, guanine, and cytosine are identified, which chemical should the nurse identify for the letter T?


  1. Cytosine
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  2. Uracil
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  3. Guanine
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  4. Thymine
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The correct answer is D. A base pair refers to two bases which form a “rung of the DNA ladder.” A DNA nucleotide is made of a molecule of sugar, a molecule of phosphoric acid, and a molecule called a base. The bases are the “letters” that spell out the genetic code. In DNA, the code letters are A, T, G, and C, which stand for the chemicals adenine, thymine, guanine, and cytosine, respectively. In base pairing, adenine always pairs with thymine, and guanine always pairs with cytosine. The other answer choices would not be the correct response to the question relating to thymine in a base pair.

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