Parent 1: AA (trait)  ×  Parent 2: aa (no trait)
Offspring: Aa (50% inherited trait)
Next generation: 50% chance of passing on

Result: Trait spreads slowly through population

Parent 1: AA (drive)  ×  Parent 2: aa (wild-type)
Offspring: AA (drive copies itself to other chromosome!)
Next generation: 100% inheritance

Mechanism:
1. CRISPR cuts wild-type chromosome
2. Cell repairs using gene drive as template
3. Both chromosomes now have gene drive
4. Result: 100% inheritance (not 50%)

Spread rate: Can reach 99% of population in 10-20 generations

Gene Drive Cassette (inserted into mosquito genome):
├─ Cas9 gene (CRISPR enzyme)
├─ Guide RNA (targets specific DNA sequence)
├─ Payload gene (sterility gene, in this case)
├─ Regulatory elements (promoters, enhancers)
└─ Homology arms (for DNA repair insertion)

Total size: ~8,000 base pairs
Location: Inserted into mosquito fertility gene
Target: Anopheles gambiae (malaria mosquito)

Safety Features:
├─ Species-specific guide RNA (should only cut Anopheles DNA)
├─ Self-limiting (designed to degrade after 20 generations)
├─ Molecular confinement (requires exact DNA match to function)
└─ Reversal drive (backup system to undo the drive if needed)

Confirmed Gene Drive Detection:
├─ Anopheles gambiae (target): 89% of population ✓ Expected
├─ Anopheles arabiensis (related mosquito): 23% ⚠ Unexpected
├─ Culex pipiens (different mosquito genus): 4% ⚠⚠ Alarming
├─ Aedes aegypti (dengue mosquito): 1.2% ⚠⚠⚠ Cross-genus jump
└─ Drosophila (fruit flies): 0.3% ⚠⚠⚠⚠ CRISIS

Traditional evolution: Genes pass parent → offspring (vertical)
HGT: Genes jump between organisms (horizontal)

Known HGT vectors:
├─ Viruses (carry DNA between hosts)
├─ Bacteria (plasmid exchange)
├─ Parasites (Wolbachia, common in insects)
└─ Direct uptake (environmental DNA)

What happened:
Wolbachia bacteria (infects 60% of insect species globally)
→ Picked up gene drive cassette from mosquito cells
→ Transferred to other insect species
→ Gene drive inserted into non-target genomes

Guide RNA designed to target mosquito fertility gene:
Target sequence: 5'-CTGACTGACTGACTGA-3' (Anopheles-specific)

But related species have similar sequences:
Culex gene: 5'-CTGACTGACTGACTGT-3' (15/16 match, 93.75%)

CRISPR Cas9 tolerance: Will cut sequences with 90%+ match
Result: "Close enough" targeting → Cross-species editing

Drosophila characteristics:
├─ Generation time: 10 days (vs mosquitoes' 30 days)
├─ Population size: Billions globally
├─ Genetic diversity: Lower than mosquitoes
├─ Result: Gene drive spread 3x faster

Within 6 months:
Drosophila gene drive prevalence: 34% globally

Insect Cascade (2052-2053):
├─ Bees (Apis mellifera): 12% carry gene drive
├─ Butterflies (Lepidoptera): 8% multiple species
├─ Beetles (Coleoptera): 4% agricultural species
├─ Wasps (Hymenoptera): 6% parasitic wasps
└─ Flies (Diptera): 23% houseflies, fruit flies

Non-Insect Detection (via HGT):
├─ Birds (insect-eating): 0.2% (gene drive in gut microbiome)
├─ Fish (aquatic insects): 0.1% (gene drive in parasites)
├─ Plants (pollinator contact): 0.03% (gene drive in associated bacteria)
└─ Soil bacteria: 0.4% (widespread environmental contamination)

Species impact assessment:
├─ Mosquitoes (target): Population down 67% ✓ Intended
├─ Fruit flies: Population down 34% ⚠ Unintended
├─ Bees: Population down 8% ⚠⚠ Pollination crisis
├─ Butterflies: Population down 12% ⚠⚠ Ecosystem disruption
└─ Agricultural pests: Population down 23% ✓ Beneficial side effect?

Cascade effects:
- Pollination services: DOWN 12% (crop yields affected)
- Insect-eating bird populations: DOWN 19% (food scarcity)
- Decomposition rates: DOWN 8% (insect decomposers affected)
- Agricultural productivity: DOWN 9% (pollination + pest dynamics)