Post-transcriptional control: Alternative splicing of RNA transcripts is well known to regulate which of the following gene products?

Introduction / Context:
Alternative splicing allows one gene to generate multiple protein isoforms by selecting different exon combinations. This mechanism diversifies proteomes and enables tissue- or stage-specific functions.

Given Data / Assumptions:

• Tachykinin family peptides arise from alternative splicing of a common precursor transcript.
• Alternative splicing affects coding sequence and peptide content.
• DNA methylation and protein dimerization (leucine zippers) are separate processes.

Concept / Approach:
In neurons and endocrine tissues, the preprotachykinin gene is differentially spliced to produce distinct neuropeptides (such as substance P and neurokinin A), illustrating classic splicing-based regulation of peptide identity.

Step-by-Step Solution:
Recognize which option references a known splicing-controlled gene → tachykinins. Exclude items not directly governed by splicing (DNA methylation patterns; leucine zipper formation is a protein structural motif). Note that tubulin genes can have multiple isoforms but the option presented incorrectly ties them “exclusively” to methylation.

Verification / Alternative check:
Literature demonstrates tissue-specific tachykinin splice variants, validating splicing as the controlling mechanism.

Why Other Options Are Wrong:
Splicing does not “regulate” methylation; leucine zippers are protein–protein interaction motifs; “none” contradicts established examples.

Common Pitfalls:
Assuming all regulation is transcriptional; conflating epigenetic DNA marks with RNA processing.

Final Answer:
Tachykinins (for example, substance P and neurokinin A from the preprotachykinin gene).