41.   In her lab she has developed a technique that uses retroviruses to induce mutations of single genes in zebra fish.

42.   In some cases, scientists are focusing on trying to find single genes or the proteins they produce to serve as markers.

43.   In the modern quest for the genetic basis of aggression, scientists are not looking for a single gene that rules.

44.   In those early days, scientists knew the function of the protein and worked backwards, taking years to isolate a single gene.

45.   In their report in Science, they describe how they have found a single gene that spurs other genes to signal the bacteria to form themselves into biofilms.

46.   It has been particularly useful for researching diseases caused by a single gene, Rauscher said.

47.   Last December, researchers at the University of Connecticut reported they had doubled the life span of a fruit fly by altering a single gene.

48.   Listeria likewise appears to rely on a single gene in co-opting actin within host cells, though the gene is completely different from the one at work in Shigella.

49.   Now, scientists think they know why, and the answer offers a rare example of a behavioral difference linked to a single gene.

50.   One is to create numerous mutations in a single gene.