Changes in Gene Regulation
Biological traits can change when existing genes are expressed at different times, places, or levels without requiring the origin of entirely new proteins.
The Investigative Question
How much biological innovation can arise through changes in gene regulation?
What We Observe
Genes operate within regulatory systems that determine when, where, and how strongly they are expressed. Mutations in regulatory DNA or regulatory proteins can therefore alter traits without changing the coding sequence of the affected gene.
Scientific Background
Developmental and physiological differences can result from changes in promoters, enhancers, transcription factors, signaling pathways, and other regulatory elements.
Why It Matters
Regulatory evolution provides a mechanism for modifying existing biological systems by changing their deployment rather than inventing every component anew.
What Is Known
Regulatory mutations can produce substantial phenotypic effects. Empirical studies have identified cis-regulatory changes associated with differences in morphology, physiology, behavior, adaptation, and development. Regulatory changes can alter when, where, or how strongly an existing gene is expressed without changing the protein encoded by that gene.
What Is Proposed
Evolutionary developmental biology proposes that changes in gene regulation have contributed importantly to morphological diversification. Some researchers have argued that cis-regulatory changes make a particularly important or predominant contribution to the evolution of form, while others argue that the evidence supports substantial roles for both regulatory and protein-coding changes.
What Remains Uncertain
For ancient developmental innovations, identifying the exact regulatory changes and reconstructing ancestral regulatory networks can be difficult. The relative contributions of regulatory changes and protein-coding changes also vary among traits and remain difficult to generalize across the history of life.
Design Relevance
Regulatory change is relevant to Intelligent Design because major phenotypic differences need not require entirely new proteins. At the same time, regulatory explanations depend upon the existence and organization of the systems being regulated.
Assessment
Changes in gene regulation are a demonstrated source of biological variation and innovation. They show that important phenotypic changes can occur by altering the deployment of existing genes rather than by changing every protein involved. Their contribution to particular major innovations should be evaluated alongside changes in protein-coding genes and the origin and organization of the underlying developmental systems.