AAMC FL Practice Exam

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Study for the AAMC FL Exam. Prepare with comprehensive flashcards and multiple-choice questions, each equipped with hints and explanations. Gear up for your medical school entrance exam!

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What is missing from the deoxyribose sugar found in DNA?

2' OH
3' OH
Oxygen atom
Methyl group

The correct answer is: 2' OH

The deoxyribose sugar in DNA is characterized by the absence of a hydroxyl group (-OH) at the 2' position of the sugar ring. Instead of having an -OH group at this position, deoxyribose possesses just a hydrogen atom, making it "deoxy," or lacking oxygen where it typically would be. This absence of the 2' hydroxyl group is significant because it distinguishes deoxyribose from ribose, the sugar found in RNA, which does contain both a 2'OH and a 3'OH group. The structural difference between deoxyribose and ribose contributes to the overall stability and function of DNA compared to RNA. Other options, such as a 3' OH, are present in deoxyribose, while references to an oxygen atom or a methyl group do not highlight the key structural difference that defines deoxyribose as lacking the 2' hydroxyl group. These elements do not play a role in the primary structural difference between the sugars in DNA and RNA.