Question

Single strands of nucleic acids are directional, meaning that there are two different ends. What functional groups define the two different ends of a strand?

1) 5' end and 3' end
2) Amino end and Carboxyl end
3) Hydroxyl end and Phosphate end
4) Purine end and Pyrimidine end

Answer 1

The ends of a nucleic acid strand are defined by the functional groups present: the 5' end has a free phosphate group, and the 3' end has a free hydroxyl group. The correct answer is the 5' end and 3' end.

Step-by-step explanation:

The two different ends of a nucleic acid strand are defined by the functional groups present at each end. At the 5' end, there is a free phosphate group, and at the 3' end, there is a free hydroxyl group. These ends give nucleic acids their directionality which is critical for processes such as DNA replication and transcription. The sequences are always written from the 5' to 3' end to maintain consistency. Hence, the answer to the student's question is (1) 5' end and 3' end.