Read the passage below regarding evolutionary developmental biology:
Paragraph 1: For much of the late twentieth century, evolutionary biologists largely operated under the assumption that morphological evolution is driven primarily by mutations in protein-coding sequence regions. This structural gene hypothesis asserted that novel physical traits arise when amino acid substitutions alter the basic biochemical properties of functional proteins.
Paragraph 2: However, recent comparative genomic studies across diverse drosophilid lineages have revealed a striking discrepancy. Researchers observed extensive anatomical divergence between closely related species whose protein-coding sequences remain virtually identical. Instead, variations were localized to non-coding cis-regulatory elements that dictate when and where invariant proteins are expressed during development.
Paragraph 3: To account for these findings, contemporary researchers have advanced the regulatory evolution model. This framework posits that evolutionary novelties stem not from altering the cellular machinery itself, but from rewiring gene regulatory networks. By modifying transcription factor binding sites, organisms can adjust spatial-temporal gene expression patterns modularly without triggering the deleterious pleiotropic effects often caused by coding-sequence mutations.
Paragraph 4: While the regulatory evolution framework successfully resolves the paradox of coding sequence conservation amidst morphological diversity, it also imposes new empirical challenges. Assessing the functional impact of non-coding mutations requires labor-intensive functional assays rather than simple sequence alignment, demanding a synthesis of bioinformatic screening and experimental embryology in future phylogenomic research.
Based on the passage, arrange the functional descriptions of the four paragraphs in the correct logical sequence corresponding to Paragraph 1 through Paragraph 4.
- 1Establishes a traditional scientific paradigm and describes its foundational mechanism.
- 2Introduces empirical findings that undermine the traditional paradigm by highlighting an unexplained contradiction.
- 3Presents a novel conceptual framework that reconciles the conflicting evidence without discarding genetic conservation.
- 4Evaluates the broader operational consequences and methodological requirements of adopting the new framework.