NURSING EXAM QUESTIONS
BIOCHEMISTRY
Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Cytosine
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Guanine
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Adenine
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None of the above
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Detailed explanation-1: -Uracil (U) is one of the four nucleotide bases in RNA, with the other three being adenine (A), cytosine (C) and guanine (G). In RNA, uracil pairs with adenine. In a DNA molecule, the nucleotide thymine (T) is used in place of uracil.
Detailed explanation-2: -In DNA, adenine always pairs with thymine (A-T), and guanine always pairs with cytosine (G-C). RNA is the same, except that adenine always pairs with uracil (A-U).
Detailed explanation-3: -Uracil pairs with adenine through hydrogen bonding. When base pairing with adenine, uracil acts as both a hydrogen bond acceptor and a hydrogen bond donor. In RNA, uracil binds with a ribose sugar to form the ribonucleoside uridine. When a phosphate attaches to uridine, uridine 5′-monophosphate is produced.
Detailed explanation-4: -In DNA adenine always pairs with thymine and cytosine always pairs with guanine. In RNA uracil replaces thymine, therefore in RNA adenine always pairs with uracil. Thymine and uracil or adenine have two hydrogen bonds between them, whereas guanine and cytosine have three.
Detailed explanation-5: -DNA base pair. Under normal circumstances, the nitrogen-containing bases adenine (A) and thymine (T) pair together, and cytosine (C) and guanine (G) pair together.