What is the key difference between DNA and RNA?

The key difference between DNA and RNA lies in their sugar components. DNA contains deoxyribose, which is a five-carbon sugar that lacks an oxygen atom at the 2' position compared to ribose. This structural difference contributes to the stability of DNA, making it a more suitable molecule for long-term storage of genetic information.

In contrast, RNA contains ribose, which has a hydroxyl (-OH) group at the 2' position, making it more reactive and less stable than DNA. This instability is advantageous for RNA during processes like transcription and translation, where short-lived molecules are needed to synthesize proteins based on the DNA template.

The other choices highlight common misconceptions or incorrect facts related to the structure of DNA and RNA. RNA is typically single-stranded, and while thymine is indeed absent in RNA, it is actually uracil that replaces thymine. Additionally, DNA is predominantly found in the nucleus, while RNA can be found both in the nucleus and in the cytoplasm, which would also be incorrect. Understanding the distinct sugar components in DNA and RNA is fundamental to grasping their respective roles in genetics and cellular functions.