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.)

Are there any evolutionary advantages to having the same DNA sequence code for two protein products? Are there any disadvantages?

Key Concepts

Alternative Splicing

Alternative splicing is a process by which a single gene can produce multiple protein isoforms by including or excluding certain exons during RNA processing. This mechanism allows for greater diversity in protein function and regulation, enabling organisms to adapt to various environmental challenges. In the context of the question, the ability of a single exon to code for two different proteins exemplifies how alternative splicing can enhance genetic versatility.

Gene Duplication and Divergence

Gene duplication is a key evolutionary mechanism where a segment of DNA is copied, resulting in two identical genes. Over time, these duplicated genes can diverge in function, leading to the evolution of new traits or functions. The phenomenon described in the question may suggest that the ability to produce two proteins from the same sequence could be a result of evolutionary pressures favoring genetic redundancy and functional specialization.

Evolutionary Trade-offs

Evolutionary trade-offs refer to the balance between advantages and disadvantages that arise from certain genetic traits. While producing multiple proteins from the same DNA sequence can provide flexibility and adaptability, it may also lead to resource allocation issues or potential misregulation of protein expression. Understanding these trade-offs is crucial for evaluating the evolutionary significance of such genetic phenomena.