M. Klemke et al. (2001) discovered an interesting coding phenomenon in which an exon within a neurologic hormone receptor gene in mammals appears to produce two different protein entities (and ALEX). The following is the DNA sequence of the exon's end derived from a rat.
  5'-gtcccaaccatgcccaccgatcttccgcctgcttctgaagATGCGGGCCCAG
The lowercase letters represent the initial coding portion for the protein, and the uppercase letters indicate the portion where the ALEX entity is initiated. (For simplicity, and to correspond with the RNA coding dictionary, it is customary to represent the coding (non-template) strand of the DNA segment.)
Convert the coding DNA sequence to the coding RNA sequence.

Verified step by step guidance

1. Step 1: Understand the problem. The task is to convert the coding DNA sequence provided into the coding RNA sequence. Remember that the coding strand of DNA is complementary to the template strand and matches the RNA sequence except that thymine (T) in DNA is replaced by uracil (U) in RNA.
2. Step 2: Identify the DNA sequence provided. The sequence is: 5'-gtcccaaccatgcccaccgatcttccgcctgcttctgaagATGCGGGCCCAG.
3. Step 3: Replace all occurrences of thymine (T) in the DNA sequence with uracil (U) to create the RNA sequence. For example, 'gtccca' becomes 'guccca'.
4. Step 4: Ensure that the RNA sequence maintains the same directionality (5' to 3') as the DNA coding strand. The uppercase letters in the sequence should remain uppercase in the RNA sequence, as they represent a specific coding region.
5. Step 5: Write out the final RNA sequence after replacing all thymine (T) with uracil (U). The sequence should now be in RNA format, ready for further analysis or use.

Key Concepts

Transcription

Transcription is the process by which the genetic information encoded in DNA is copied into messenger RNA (mRNA). During transcription, RNA polymerase binds to the DNA at the promoter region and synthesizes a single strand of RNA complementary to the DNA template strand. In this case, the coding DNA sequence is transcribed into RNA, replacing thymine (T) with uracil (U) in the RNA sequence.

Exons and Introns

Exons are the coding regions of a gene that are retained in the final mRNA after the splicing process, while introns are non-coding regions that are removed. In the context of the question, the exon mentioned is responsible for producing two different protein entities, indicating that alternative splicing may occur, allowing for the generation of multiple proteins from a single gene. Understanding the distinction between exons and introns is crucial for interpreting the coding sequence.

Alternative Splicing

Alternative splicing is a regulatory mechanism that allows a single gene to produce multiple mRNA variants by including or excluding certain exons during the splicing process. This phenomenon can lead to the production of different protein isoforms, such as the two entities mentioned (and ALEX) in the question. Recognizing how alternative splicing contributes to protein diversity is essential for understanding the complexity of gene expression and function.