Description of Genetics Cancers develop because of alterations, or mutations, in genes that normally promote controlled cell growth. Most cancers are caused by mutations that occur only in the tissue that is affected by the cancer. Description of Genes Each cell in your body contains about 25,000 genes, which determine your hair color, your height, and other characteristics that make you unique. Autosomal Dominant Inheritance A mutation is a change in a gene that prevents it from working properly. We inherit mutations from our parents in specific ways, one of which is called autosomal dominant inheritance. Autosomal Recessive Inheritance This type of genetic inheritance means that both copies of the gene must have a mutation for a person to have the trait. One copy of the mutation is inherited from the mother, and the other from the father. A person who has only one recessive gene mutation is a "carrier" for the trait or disease, but he or she does not have any health problems from carrying this one mutation. X-Linked Inheritance X-linked inheritance means that the gene alteration causing the trait or the disorder is located on the X chromosome. Females have two X chromosomes, and males have one X and one Y. Mutations in X chromosome genes can be recessive or dominant. Multifactorial Inheritance Multifactorial inheritance means that many factors are involved in causing a health problem. The factors are usually both genetic and environmental, where a combination of genes from both parents, in addition to unknown environmental factors, produce the trait or condition. Features of Inherited Cancers A family medical history helps determine whether relatives have an increased chance of developing specific types of cancer, how great the risk of cancer might be, and whether genetic testing might be useful. Genetic Services for Cancer Diagnosis: When, Where, How If you have a family history of multiple cases of the same or related types of cancer, you may need genetic counseling. Generally, you can find genetic counseling and other genetic services at large hospitals or medical centers. How Genes Cause Cancer Genes that have alterations, or mutations, can cause cells to become cancerous. Some mutations are inherited and others are "acquired," occurring by chance over time.