In a DNA the coding region reads 5′-CGT-3′. This would code in the RNA as:
**Core Concept**
The genetic code is a set of rules used by living cells to translate information encoded within genetic material (DNA or RNA) into proteins. During transcription, the DNA sequence is transcribed into a complementary RNA sequence, with the exception of thymine (T) in DNA being replaced by uracil (U) in RNA.
**Why the Correct Answer is Right**
The given DNA sequence 5'-CGT-3' will be transcribed into a complementary RNA sequence. In RNA, the base pairing rules are the same as in DNA, but with the exception that thymine (T) in DNA is replaced by uracil (U) in RNA. Therefore, the RNA sequence will have cytosine (C) paired with guanine (G), guanine (G) paired with cytosine (C), and thymine (T) in DNA is replaced by uracil (U) in RNA. Thus, the RNA sequence will be 5'-GCU-3'.
**Why Each Wrong Option is Incorrect**
* **Option A:** Not applicable, as this is the correct answer.
* **Option B:** This is incorrect because the correct RNA sequence is 5'-GCU-3', not 5'-GCA-3'.
* **Option C:** This is incorrect because the correct RNA sequence is 5'-GCU-3', not 5'-GCT-3'.
* **Option D:** This is incorrect because the correct RNA sequence is 5'-GCU-3', not 5'-GCU-3'.
**Clinical Pearl / High-Yield Fact**
Remember the base pairing rules for transcription: A-T in DNA becomes A-U in RNA, and G-C in DNA becomes G-C in RNA. This is essential for understanding the process of transcription and the relationship between DNA and RNA.
**Correct Answer:** B. 5'-GCU-3'.