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). 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?

Key Concepts

Exons and Introns

Exons are the coding regions of a gene that are transcribed into mRNA and translated into 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, especially in cases where alternative splicing can lead to different protein products from the same gene.

Translation and Amino Acid Sequence

Translation is the process by which ribosomes synthesize proteins using the mRNA sequence as a template. Each set of three nucleotides, known as a codon, corresponds to a specific amino acid. By translating the provided DNA sequence into its corresponding mRNA and then into an amino acid sequence, one can determine the proteins produced by the gene and compare them for similarities or differences.

Alternative Splicing

Alternative splicing is a regulatory mechanism that allows a single gene to produce multiple protein isoforms by including or excluding certain exons during mRNA processing. This phenomenon can lead to the production of distinct proteins, such as the two entities mentioned in the question, and is essential for understanding the complexity of gene expression and protein diversity in organisms.