A Common Source of DNA Damage Is the Spontaneous Loss

question 138

Multiple Choice

A common source of DNA damage is the spontaneous loss of the amine group on cytosine, which then transforms into uracil. This occurs at a rate of about 100 times a day. Fortunately, the body produces enzymes able to detect and repair such uracils back into cytosine. Given this information, suggest why DNA differs from RNA in possessing the nucleotide thymine rather than uracil.

• A)If these thymines were uracils, then they would be promptly changed into cytosines.
• B)The DNA has thymine instead of uracil so as to maintain four different types of nitrogenous bases.
• C)The additional carbon that distinguishes thymine from uracil is apparently the label that prevents the conversion of this nucleotide back into cytosine.
• D)all of the above

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