Definition
Molecular drive is a term in evolutionary biology describing a class of non-Mendelian processes that cause the rapid spread and fixation of specific genetic elements throughout a population’s genome, independent of natural selection.
Overview
The concept was introduced by geneticist Gabriel Dover in 2000 to explain phenomena that could not be adequately accounted for by traditional models of genetic drift, selection, or gene flow. Molecular drive encompasses mechanisms such as gene conversion, unequal crossing‑over, transposable element proliferation, and the concerted evolution of multigene families. These mechanisms can lead to homogenization of DNA sequences across multiple loci and between chromosomes, resulting in rapid genomic changes that may appear selective but are actually driven by intrinsic molecular processes.
Etymology / Origin
The phrase combines “molecular,” referring to processes at the DNA or chromosomal level, with “drive,” a term historically used in genetics (e.g., “meiotic drive”) to denote biased transmission of alleles. Dover coined “molecular drive” to parallel “meiotic drive” while emphasizing that the driving force originates from molecular mechanisms rather than gametic segregation.
Characteristics
| Feature | Description |
|---|---|
| Mechanistic Basis | Operates through DNA-level events such as gene conversion, template switching, replication slippage, and transposition. |
| Population Effect | Can cause near‑fixation of a particular DNA sequence across the entire population, often much faster than expected under neutral drift. |
| Independence from Selection | May spread regardless of whether the sequence confers a fitness advantage; selection can later act upon the resulting genomic configuration. |
| Examples | • Concerted evolution of ribosomal RNA gene clusters. • Spread of the 5S rRNA gene family via unequal crossing‑over. • Proliferation of the P element transposon in Drosophila melanogaster. |
| Distinction from Meiotic Drive | Meiotic drive biases the segregation of whole chromosomes or alleles during meiosis; molecular drive acts on sub‑chromosomal DNA sequences and often during mitotic or recombination events. |
| Evolutionary Implications | Provides a mechanism for rapid genomic restructuring, contributes to the emergence of new gene families, and influences the maintenance of genomic integrity. |
Related Topics
- Meiotic drive – biased inheritance of chromosomes or alleles during meiosis.
- Gene conversion – non‑reciprocal transfer of DNA sequence information between homologous regions.
- Unequal crossing‑over – recombination event leading to duplication or deletion of DNA segments.
- Transposable elements – DNA sequences capable of moving within the genome, often participating in molecular drive.
- Concerted evolution – coordinated evolution of multiple copies of a gene or repeat sequence, frequently driven by molecular drive mechanisms.
- Neutral theory of molecular evolution – framework describing the role of genetic drift and neutral mutations, which molecular drive can complement or contrast.