Researchers can use DNA samples to look at whether parents and their children have certain types of genes. Studying the relative importance of genes and other factors helps researchers to understand differences in young people’s development, health, behaviour, growth and learning. For instance, recent research has identified genes associated with common allergies including pollen, dust-mite and cat allergies. It is believed that allergies are very often passed from one generation to the next. Understanding the genetic factors underlying allergies may be key to understanding who might be most likely to suffer from allergies and how this very common condition might best be treated.