Genetic diseases, as defined by The University of Utah, are either a mutation in one gene, or the addition or subtraction of a chromosome or set of chromosomes. Examples of genetic diseases include various cancers and Down syndrome. No one can control his genetics; however, it is possible for parents to decide if the genetic risk is too great to have a child, increasing this child's risk of developing certain diseases.
Colorectal Cancer (Colon Cancer)
Those with a family history of colorectal cancer have an increased risk of developing the disease themselves. This risk is greater when a family member is diagnosed with this disease before the age of 50, according to The University of Utah.
Genetics play a role in this when family members have inherited one of two rare genes: FAP (familial adenomatous polyposis) or HNPCC (hereditary non-polyposis colon cancer).
FAP prevents uncontrolled cell growth, while HNPCC is caused by mutations in one or more genes which are unable to repair DNA that are damaged. When either of these occurs, cancerous cells are able to grow and multiply. Should a parent carry either of these genes, her children are 50 percent more likely to develop colon cancer.
Down Syndrome
Also referred to as "trisomy 21," Down syndrome is caused by an extra copy of chromosome 21, as The University of Utah explains. This disease affects between one in 800 and one in 1,000 infants each year, according to the National Human Genome Research Institute website.
When there is an extra copy of chromosome 21, each gene in the chromosomes may produce more protein than normal. This excess protein results in serious health complications such as learning difficulties, poor muscle tone during infancy, mental retardation and the distinct facial appearance seen in children and adults with this disease.
Additional health risks for those with Down syndrome include an increased risk of heart defects, loss of hearing and digestive problems that include celiac disease or gastroesophageal reflux.
The risk of having a baby with Down syndrome is greater in women 35 and older because of a condition called nondisjunction, when the pair of chromosome 21 fails to separate while the egg is forming. This tends to occur more frequently in older women, according to The University of Utah.
Cystic Fibrosis
Cystic fibrosis, according to The University of Utah, is a genetic disorder affecting the respiratory and digestive systems. It is the most common, fatal genetic disease in the United States, affecting approximately 30,000 people.
Those with this disease inherit a defective gene on chromosome seven. This chromosome is called CFTR (cystic fibrosis transmembrane conductance regulator). When working properly, the protein this gene aids salt movement in and out of cells. However when defective, this movement is blocked, resulting in the production of an abnormally thick mucous on the outside of the cell wall. The lungs are affected the most by this mucous, as it clogs the airways of the lungs, increasing the risk of infection due to the bacteria the mucous contains.
The National Human Genome Research Institute adds that this production of mucous also blocks the pancreas, preventing the necessary enzymes from reaching the intestines. These enzymes are required to digest food.
For a child to get cystic fibrosis, both parents must have, and pass on, the defective gene. In cases where only one parent has the faulty gene, that child becomes a carrier of cystic fibrosis but does not have the disease. These children can pass the disease to their children should their mate be a carrier as well.
