Aim to identify people without symptoms who carrier a genetic condition, so that these individuals can be informed about their health and reproductive risk. This is called cascade screening, which usually starts with one affected family member Examples of conditions screened in populations:

• Thalassemia, an autosomal recessive condition. When both members of a couple are found to be carriers of an autosomal recessive condition, they have a one in four chance of having an affected child. Premarital and cascade carrier screening programs are conducted in several countries to reduce the birth of children with genetic conditions.
• Hypercholesterolemia, an autosomal dominant condition--The risk is accompanied by a genetically determined elevated high cholesterol level, which may be reduced by preventive measures, such as diet and medications