Glossary of gene drive terminology
(The explanations below are mostly generated by ChatGPT and now manually reviewing & editing. Please feel free to report any mistakes or suggestions.)
A
- Aedes: A genus of mosquitoes including important disease vectors such as Aedes aegypti.
- Anopheles: A genus of mosquitoes that transmit malaria, such as Anopheles gambiae.
C
- Carrying capacity: The maximum population size an environment can sustain.
- Cas9 (CRISPR-associated protein 9): An RNA-guided DNA endonuclease used in CRISPR systems to introduce site-specific cuts in the genome.
- Chasing: A spatial dynamic in which drive-free or resistance-carrying individuals escape the suppression zone and recolonize cleared areas, preventing complete population elimination.
- Confinement: The restriction of a gene drive to a defined spatial area. If a drive is confined, it has an invasion threshold that prevents the drive from spreading if migrated to untargeted regions.
- CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats): A genome editing system that enables targeted DNA cleavage and repair.
- Culex: A genus of mosquitoes including Culex quinquefasciatus, a vector of various viruses.
D
- Daisy-chain drive: A self-exhausting gene drive system composed of multiple linked elements.
- Density-dependent competition: Competition intensity increases with population density.
- Deterministic model: A model where population outcomes are fully determined by parameters.
- Discrete-generation model: A model assuming non-overlapping generations.
- Drive conversion (Drive efficiency): The rate at which a drive allele converts its wild-type counterpart.
- Drosophila melanogaster: A model organism widely used in genetics and drive research.
E
- Effective population size ($N_e$): The size of an idealized population with equivalent genetic drift.
- Embryo resistance formation (maternal deposition): Resistance generated by maternal Cas9 deposition.
- End-joining repair (NHEJ): A DNA repair pathway that often produces mutations at cut sites.
F
- Fecundity: The number of offspring produced per female.
- Fertility: The ability to produce viable offspring.
- Fitness: The relative reproductive success of a genotype.
- Fraction-based model: A population model using allele frequencies rather than individuals.
- Functional resistance (r1) allele: Resistance alleles that preserve gene function while blocking the drive.
G
- Gene drive: A genetic system that biases inheritance to increase allele frequency in a population.
- Genetic drift: Random changes in allele frequency due to sampling effects.
- Genetic load: Reduction in population fitness due to deleterious alleles.
- Germline resistance formation: Resistance occurring during germline end-joining repair.
- gRNA (guide RNA): An RNA molecule that guides Cas9 to a specific DNA target sequence for cleavage.
H
- Haploinsufficient (haplolethal): A gene where one functional copy is insufficient for viability.
- Haplosufficient (recessive lethal): A gene where heterozygotes are viable but homozygotes are lethal.
- Heterozygote advantage: Heterozygotes have higher fitness than homozygotes.
- Homing drive: A CRISPR-based drive that cuts and copies itself via HDR.
- Homology-directed repair (HDR): A high-fidelity repair mechanism using a homologous template.
I
- Individual-based model: A model that tracks each organism and its genotype explicitly.
- Invasion threshold: Minimum initial drive frequency required for spread.
L
- Low-density growth rate: Population growth rate when density is close to zero, where density-dependent competition can be neglected.
M
- Mendelian inheritance: Standard 50% allele transmission to offspring.
- Meiosis: The process of cell division in sexually reproducing organisms that produces gametes (sperm or eggs) with half the chromosome number of the parent, allowing genetic recombination and inheritance.
- Migration rate: The proportion of individuals moving between populations per generation.
N
- Nonfunctional resistance (r2) allele: Resistance alleles that disrupt gene function.
O
- Overlapping-generation model: A model where individuals of different ages coexist.
P
- Panmictic model: A model assuming random mating across the entire population.
- Population genetic control: The use of genetic strategies to alter, suppress, or regulate populations.
- Population modification: Population genetic control strategies aiming to alter genetic traits of a population without necessarily reducing its size.
- Population suppression: Population genetic control strategies intended to reduce population size, growth, or persistence, potentially leading to local elimination.
- Promoter: DNA element controlling expression of a downstream gene.
R
- Release of insects carrying dominant lethal alleles (RIDL): A genetic control strategy using sterile insects.
- Rescue element: A gene component that restores viability to individuals carrying a drive.
- Resistance allele: An allele preventing the homing drive from cutting or copying.
S
- Self-sustaining drive: A drive that can persist and spread indefinitely once released.
- Self-limiting drive: A drive designed to fade out after several generations.
- Sexual selection: Differential mating success based on genotype or phenotype.
- SLiM: A forward genetic simulation framework for population modeling.
- Spatial model: A model incorporating spatial structure or movement.
- Stochastic model: A model incorporating randomness in reproduction or migration.
T
- Target site: DNA sequence recognized and cleaved by Cas9/gRNA.
- Toxin-antidote drive: A system that targets and disrupts an essential gene while also providing rescue via a recoded version of the target, including designs such as TARE, TADE, TADS, etc.
- Cleavage rate: Success rate of target DNA cleavage.
U
- Underdominance drive: A drive where heterozygotes have lower fitness than homozygotes.
V
- Vector-borne disease: Diseases transmitted by organisms such as mosquitoes.
- Viability: The ability of individuals to survive to reproductive age.
W
- Wolbachia: A maternally transmitted bacterium affecting host reproduction.
- Wright–Fisher model: A panmictic discrete-generation genetic drift model with constant population size.
X
- X-shredder: A system that destroys the X chromosome during sperm formation, biasing sex ratio.