Gene Duplication and New Functions
Gene duplication creates additional copies of genetic material that can subsequently diverge in sequence, regulation, and function.
The Investigative Question
Can duplicated genes acquire new biological functions, and how does that process occur?
What We Observe
Genomes contain many families of related genes. Duplication can produce an additional gene copy while another copy continues to perform an existing function.
Scientific Background
Duplicated genes may be lost, retain overlapping functions, divide ancestral functions, or acquire altered functions. Different evolutionary models describe how duplicated copies are preserved and diverge.
Why It Matters
Gene duplication is frequently proposed as an important source of evolutionary innovation because it creates additional genetic material that can follow different evolutionary paths. Duplicate copies may be lost, preserved by dosage or other selective effects, divide ancestral functions, or undergo functional divergence.
What Is Known
Gene duplication occurs, and many genomes contain duplicated genes with related but distinct functions. Comparative studies provide evidence for functional divergence following duplication. Experimental work has also demonstrated a pathway in which a gene with weak secondary activity was amplified and different copies subsequently accumulated mutations that increased their functional specialization.
What Is Proposed
Several models describe how duplicate genes can be retained and acquire specialized or novel functions. These include neofunctionalization, subdivision of ancestral functions, selection involving gene dosage, and pathways in which an existing secondary activity is amplified and subsequently improved.
What Remains Uncertain
The exact historical sequence by which a particular ancient gene family acquired its present functions is not always recoverable, and different models may fit the available evidence. The relative importance of the different duplication pathways across the history of life also remains an empirical question.
Design Relevance
Gene duplication is directly relevant to claims that evolutionary mechanisms cannot generate new functional information. The important question is what kinds of new functions duplication and divergence have actually been shown to produce.
Assessment
Gene duplication provides additional genetic material and can be followed by functional divergence. Experimental evidence shows that amplification and subsequent mutation can produce increasingly specialized gene copies when useful activities are already present. Other models allow different routes to functional change. The contribution of gene duplication to particular major biological innovations should therefore be evaluated from the specific genetic and functional evidence rather than assumed from the existence of duplication alone.