11.   And some still do not think it is wise to test couples routinely unless they have reason to think they might have the gene.

12.   Another example is women who learn they have the gene that predisposes them to breast cancer.

13.   All men have this gene, but for some inexplicable reason, black men have shorter versions of a key component called the CAG repeats.

14.   But human cells have a gene whose product, called telomerase, can lengthen telomeres.

15.   But they do have genes, as humans do.

16.   But Vega, as it turned out, did have musical genes.

17.   Caldwell, who went for genetic testing, learned eight years ago that she had the gene for the disease.

18.   Current theory holds that some people may have genes that make them particularly susceptible.

19.   Either you lack the gene responsible for being right-handed, or you have the gene but something goes wrong during development that prevents the gene from being expressed.

20.   Finally, they will ask whether people who have those genes also have predispositions to the behavior being studied.