Understand Genetics Handbook

An Overview of Genetic Disorders

As we unlock the secrets of the human genome, we're learning that nearly all diseases have a genetic component. Some, including many cancers, are caused by a mutation in a gene or group of genes in the cells of an individual. Such mutations can occur randomly or due to exposure to some environmental insult.

Other genetic disorders are hereditary - such as Huntington's disease or Tay-Sachs disease - where a mutated gene is passed down through a family and each generation of children can inherit the gene that causes the disease.

But most genetic disorders are "multifactorial inheritance disorders," meaning they are caused by a combination of small variations in genes, often in concert with environmental factors.

Through research on the human genome, we now know that many common diseases usually caused by genetic alterations in the genes of an individual's cells - such as breast cancer and colon cancer - also have rare hereditary forms. In these cases, gene variants that cause or strongly predispose a person to these cancers run in a family and significantly increase each member's risk of developing the disease.

This Genetics Handbook provides some basic information about genetics in clear language.

The Basics: Genes and How They Work

Mutations and Health

Inheriting Genetic Conditions

Genetic Consultation

Genetic Testing

Gene Therapy

The Human Genome Project and Genomic Research

A-Z of Genetic Diseases and Conditions

A-Z of Gene Symbols