Which sequence correctly represents a single strand of RNA bases (written 5′ to 3′)?

• A. 3′-A U G C-5′
• B. 5′-A U G C-3′
• C. 5′-A U G C-5′
• D. 5′-A T G C-3′

Answer: (B)

Verified step by step guidance

1. Understand that RNA sequences are conventionally written from the 5′ end to the 3′ end, which indicates the directionality of the strand.
2. Identify that the problem asks for a single strand of RNA bases written 5′ to 3′, so the sequence must start with the 5′ end and end with the 3′ end.
3. Recognize that RNA bases include adenine (A), uracil (U), guanine (G), and cytosine (C). Note that thymine (T) is not found in RNA; it is replaced by uracil.
4. Evaluate each given sequence to check if it is written 5′ to 3′ and contains only RNA bases (A, U, G, C). For example, a sequence starting with 3′ is written in the wrong direction, and any sequence containing T is DNA, not RNA.
5. Select the sequence that is written 5′ to 3′ and contains only RNA bases, which correctly represents a single strand of RNA.