How Are New Genes Created?

New genes are created through a variety of molecular mechanisms that introduce genetic novelty into genomes over evolutionary time. Here are the main ways new genes arise:

1. Gene Duplication

A copy of an existing gene is made, and then one copy can accumulate mutations and evolve a new function.

• Mechanism: Unequal crossing over, retrotransposition, or whole genome duplication.

• Outcome: One copy maintains the original function; the other is free to diverge (neofunctionalization), or both copies may specialize (subfunctionalization).

2. Exon Shuffling

Exons (the coding regions of genes) can be rearranged or recombined to create a gene with new functions.

• Mechanism: Recombination events between introns or transposons.

• Outcome: Proteins with new domain architectures and functions.

3. De Novo Gene Birth

Completely new genes can evolve from previously non-coding DNA.

• Mechanism: Random mutations create an open reading frame (ORF), and regulatory elements (e.g. promoters) evolve to express it.

• Outcome: A brand new gene not derived from any existing gene.

4. Horizontal Gene Transfer (HGT)

Genes are acquired from other species, especially common in bacteria.

• Mechanism: Transformation, transduction (via viruses), or conjugation.

• Outcome: Rapid acquisition of new traits (e.g., antibiotic resistance).

5. Gene Fusion or Fission

New genes can form by joining two separate genes or splitting one into parts.

• Fusion: Two genes merge into a single unit with new functions.

• Fission: One gene splits, and each part may evolve separately.

6. Retroposition (Retroduplication)

An mRNA transcript is reverse-transcribed and inserted back into the genome, often creating a gene copy without introns.

• Mechanism: Reverse transcription by retrotransposons.

• Outcome: A processed gene duplicate that may evolve new functions if expressed.

Summary: