11.   As if we have some kind of defective gene that makes us cheer louder for our own.

12.   Because of defective genes, they lacked a necessary enzyme in their bodies.

13.   A victim must inherit two defective genes, one from each parent, for the disorder to develop.

14.   But males, who carry one Y chromosome and one X chromosome, suffer much more severe consequences if they inherit a defective gene on their lone X chromosome.

15.   By contrast, diseases caused by a single defective gene could, at least in theory, be cured by gene therapy.

16.   Defective genes failed to produce a necessary enzyme in their bodies.

17.   Earlier attempts at gene therapy for other diseases tried to compensate for defective genes by giving patients normal versions of those genes.

18.   Gene therapy is being developed by scientists as a way to replace a defective gene in a patient with a genetic disease.

19.   Genetic tests confirmed that the woman carried the defective gene, Lewis said.

20.   Genetic testing, a relatively new field, is used to identify defective genes linked to specific diseases.