21.   The repair gene causes proteins called neurotrophins to be made.

22.   The theory is that a single gene causes a disease or a disorder.

23.   The scientists warn against embarking on such a screening effort until scientists can determine the precise risk the gene causes in a given individual.

24.   Other work has shown that a malfunctioning hairless gene can cause another hair-loss disorder, called papular atrichia.

25.   A major concern of scientists is making sure transplanted genes do not cause allergic reactions.

26.   And scientists are scrambling to figure out just how the flawed gene causes trouble.

27.   Autopsies later showed the gene caused brain cells to make dopamine and halted the normal degeneration of brain cells.

28.   He said, for example, that another gene might cause a predisposition to heart disease, and the Grinkov variant might simply accompany that gene.

29.   Most genetic disease is caused by genes that have some other beneficial purpose.

30.   Other flawed genes apparently cause the disease in other ethnic groups, the second study found.