31.   Some have suggested, he said, that these genes, when present in a single copy, protect against tuberculosis.

32.   Studies in animals, he said, suggest that people who inherit a single copy of the cystic fibrosis gene might be protected from cholera.

33.   That law allowed individuals to make a single digital copy of a copyrighted recording for personal use, but barred further copying and distribution of the recording to others.

34.   The writer whose books sell in single copies can afford to work at his own pace.

35.   These studies were the basis of the estimates that a single copy of the ATM gene increases cancer risk several fold.

36.   Though some people flip through the glossy picture book, the store still has not sold a single copy.

37.   Those individuals, it now seems, might have inherited only a single copy of the defective gene from one parent.

38.   Scientists can then find hybrids that contain a single copy of particular chromosomes.

39.   The Times said in May that it would stop using employees to distribute single copies of the paper, instead going with independent companies.

40.   Women with a single copy are five times more likely to have breast cancer, experts say.