Defective genes

Genetic disorders are caused by missing or abnormal genes. Sometimes only these defective genes are responsible for disorders, but more often than not, they are compounded by environmental factors.

	Karyotype of a man with Down syndrome.

Your genes play a role in most of the illnesses that affect you. Some of these illnesses can be attributed to an anomaly in one gene. They are called monogenic. This is the case with cystic fibrosis. Other diseases such as cancer, or conditions like dyslexia, are the result of several genes interacting with environmental factors, including diet and lifestyle. These genes are called susceptibility genes. Researchers say we all carry several such genes.