Silent cholinesterase gene: three homozygotes in a small Caucasian population.

Three sera, showing only a 2-3% of the usual cholinesterase activity and belonging to two families of 800 Caucasian inhabitants of the same small town, were classified as type II silent cholinesterase genes by polyacrylamide slab gel electrophoresis, dibucaine and fluoride number and by their specific activity with acetyl- butyryl- or propionyl-thiocholine.