The Origin of New Genes
New genes can arise through several mechanisms, including duplication and modification of existing genes and, in some cases, from previously noncoding DNA.
The Investigative Question
How do genuinely new genes arise?
What We Observe
Comparative genomics has identified genes with different evolutionary histories. Many new genes appear related to older genes, while others have been proposed to arise from sequences that were previously noncoding.
Scientific Background
Proposed mechanisms of gene birth include duplication, fusion and fission, horizontal transfer, exon rearrangement, retroposition, and de novo emergence from noncoding sequence.
Why It Matters
The origin of new genes bears directly upon questions about the generation of new biological functions and genetic information.
What Is Known
New genes arise through multiple mechanisms. Gene duplication is a major source, and evidence also supports de novo emergence of some genes from previously noncoding sequences.
What Is Proposed
For de novo gene birth, researchers propose intermediate stages rather than the sudden appearance of a complete modern gene. Previously non-genic sequences may become transcribed and translated, producing open reading frames that can function as proto-genes. Some may then be retained, modified, regulated, and eventually incorporated into established biological functions.
What Remains Uncertain
Identifying very young genes and establishing their exact ancestry can be difficult. Lack of detectable homology alone does not demonstrate de novo origin, because an older gene may have changed beyond easy recognition. Proposed de novo genes therefore require careful comparison with related genomes and corresponding ancestral sequences. The functional significance and evolutionary history of candidate proto-genes must also be established rather than assumed from transcription or translation alone.
Design Relevance
Claims about the origin of new genetic information should be tested against the growing empirical literature on gene birth rather than assuming either that new genes cannot arise naturally or that every proposed origin has been completely reconstructed.
Assessment
New genes can arise through several mechanisms. Most annotated new genes appear to have duplication-related origins, while evidence also supports the de novo origin of some genes from ancestrally non-genic sequences. Studies of proto-genes provide a plausible and testable pathway involving intermediate stages rather than the sudden appearance of a complete functional gene. Individual claims about new-gene origin should nevertheless be evaluated from comparative, genetic, and functional evidence because reconstructing the ancestry of young genes can be difficult.