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.)
Provide the amino acid sequence for each coding sequence. In the region of overlap, are the two amino acid sequences the same?

Verified step by step guidance

1. Step 1: Identify the coding (non-template) strand of the DNA sequence provided. The sequence is: 5'-gtcccaaccatgcccaccgatcttccgcctgcttctgaagATGCGGGCCCAG. Lowercase letters represent the initial coding portion for the protein, and uppercase letters represent the portion where the ALEX entity is initiated.
2. Step 2: Transcribe the DNA sequence into mRNA. Replace each thymine (T) in the DNA sequence with uracil (U) to form the mRNA sequence. For example, the lowercase portion will transcribe to mRNA as: 5'-gucccaaccaugcccaccgaucuuccgccugc... and the uppercase portion will transcribe as: 5'-AUGCGGGCCCAG.
3. Step 3: Divide the mRNA sequence into codons (groups of three nucleotides). For example, the lowercase portion will be divided into codons such as: guc, cca, acc, aug, etc., and the uppercase portion will start with AUG, CGG, GCC, etc.
4. Step 4: Use the genetic code table to translate each codon into its corresponding amino acid. For example, AUG codes for Methionine (M), CGG codes for Arginine (R), and so on. Perform this translation for both the lowercase coding sequence and the uppercase coding sequence.
5. Step 5: Compare the amino acid sequences derived from the overlapping region of the two coding sequences. Determine whether the amino acid sequences are identical or different in the region of overlap by analyzing the codons and their translations.

Key Concepts

Exons and Introns

Exons are the coding regions of a gene that are expressed as proteins, while introns are non-coding regions that are removed during RNA processing. Understanding the distinction between exons and introns is crucial for analyzing gene expression and protein synthesis, as only exons contribute to the final mRNA and subsequently the amino acid sequence of proteins.

Codons and Amino Acids

Codons are sequences of three nucleotides in mRNA that correspond to specific amino acids during protein synthesis. Each codon is translated into an amino acid by the ribosome, and understanding the genetic code is essential for determining the amino acid sequence from a given DNA or RNA sequence, particularly in the context of alternative splicing or overlapping coding regions.

Alternative Splicing

Alternative splicing is a process by which a single gene can produce multiple protein variants by including or excluding certain exons during mRNA processing. This phenomenon allows for greater diversity in protein function and regulation, and is particularly relevant in the context of the question, as it may explain how two different protein entities can arise from the same exon.