51.   One of the problems with using genetic testing to predict disease is that most genetic diseases are not determined exclusively by the presence of a single gene.

52.   Others said that what amazed them was that a single gene could so profoundly affect the length of life.

53.   Single human genes are put in animals routinely in research.

54.   Studies of evolution, Lenski explained, have often focused on the effect of mutations of a single gene.

55.   Such genes have often been for rare inherited diseases, in which a defect in a single gene is at fault.

56.   That single gene also is in the synthetic form and does not have the ability to replicate itself and produce HIV, he said.

57.   The cross-breeding approach is based on the assumption that apomixis is controlled by a single gene or a group of genes that are inherited together.

58.   The discovery of single genes that affect life span has come as a surprise to evolutionary biologists.

59.   The finding was made by means of knock-out mice, animals in which a single gene has been removed or knocked out by genetic engineering.

60.   The dream of tracing each human trait to a single gene is an old one.