IN a possible breakthrough which may pave the way for a cure for somnambulism, scientists claim to have identified the 'genetic code which makes some people sleepwalk. An international team has claimed that sufferers share a faulty chromosome which is responsible for their behaviour while asleep; by studying four generations of the same family, the scientists traced the fault to a section of chromosome 20. Carrying even one copy of the defective DNA is enough to cause sleepwalking and having isolated the defective section of genetic code, they hope to find new treatments for the condition, the Neurology journal reported. For the study, the team, led by Christina Gurnett of Washington University School of Medicine, sought the help of a large family of sleepwalkers. The family had been referred to them because one of the youngest members, a 12-year-old girl called Hannah, had been experiencing particularly troublesome sleepwalking, which regularly caused her to leave the house during the night. Using saliva samples, the researchers analysed the familys DNA to unpick the genetics of the condition. They found the problem stemmed from genetic code in chromosome 20 and this code had been passed down from generation to generation.TOI