Q.Do you think that the alternate splicing of exons may enable a structural gene to code for several isoproteins from one and the same gene? If yes, how? If not, why so?

Yes, alternate splicing of exons enables a structural gene to code for several isoproteins from one and the same gene.

In eukaryotic genes, the coding sequences (exons) are interrupted by non-coding sequences (introns). During post-transcriptional processing, the primary RNA transcript undergoes splicing, where introns are removed, and exons are joined together. Alternate splicing is a mechanism where different combinations of exons from the same primary transcript are selectively included or excluded. This process generates multiple distinct messenger RNA molecules from a single gene. Each of these different mRNA molecules can then be translated into a unique protein isoform, or isoprotein, t …

In eukaryotic organisms, the journey from a gene to a functional protein is a multi-step process, beginning with transcription and followed by various post-transcriptional modifications. One of the most crucial of these modifications is splicing, which plays a significant role in shaping the final messenger RNA (mRNA) molecule.

Genes in eukaryotes are often "split," meaning they contain both coding sequences called exons and non-coding intervening sequences called introns. After a gene is transcribed into a primary RNA transcript (also known as heterogeneous nuclear RNA or hnRNA), the introns must be removed, and the exons must be precisely joined together to form a mature, functional mRNA molecule. This process ensures that only the relevant coding information is present for protein synthesis.

Normally, splicing machinery identifies specific splice sites at the boundaries of introns and exons, excising the introns and ligating the exons in a fixed order. However, the fascinating aspect of gene expression is that this process is not always rigid.

Alternate splicing is a sophisticated regulatory mechanism where different combinations of exons from the same primary RNA transcript are selected and joined together to form multiple distinct mature mRNA molecules. Instead of always including every exon in the same sequence, the cellular machinery can selectively include or exclude certain exons, or even use alternative splice sites within an exon or intron.

Here's how this enables a single structural gene to code for several isoproteins:

• Different mRNA Transcripts: From a single primary RNA transcript, alternate splicing can generate several different mature mRNA molecules. Each of these mRNA molecules will have a unique sequence of exons.
• Unique Amino Acid Sequences: When these different mRNA molecules are translated into proteins, their distinct exon combinations lead to different sequences of amino acids. …

Think of splicing as combinatorics rather than only describing it qualitatively: if a primary transcript has several exons and splicing can choose to include or skip a subset of them, the number of possible exon combinations -- and therefore possible mature mRNAs -- grows quickly even from a modest number of exons. This numerical angle makes it intuitive why a genome with far fewer gene …