Humans and animals have highly sophisticated nervous systems, which are unfortunately often prone to illness and disease. A plethora of factors may be responsible for problems but there is increasing evidence of genetic causes for a number of conditions. Species or races with relatively small populations are known to be particularly prone to genetic problems. An example is the Tyrolean Grey, a cattle breed represented by only about 5,000 registered cows and known to be susceptible to a particular neurological disorder. Scientists have now uncovered the genetic basis for the condition.