genetic disorder
A genetic disorder is a disease caused wholly or partly by a change in a person's DNA, the body's instruction manual. If a recipe in that manual is misprinted, the protein it specifies may be missing, faulty or made at the wrong time, and the body can develop or function abnormally as a result. The change may be inherited from a parent or arise new in the affected person.
Genetic disorders come in several broad types. Single-gene (Mendelian) disorders, like cystic fibrosis or Huntington disease, stem from one faulty gene and follow recognizable inheritance patterns. Chromosomal disorders, like Down syndrome, involve whole missing, extra or rearranged chromosomes. Complex or multifactorial disorders, like many cases of heart disease or diabetes, arise from many genes acting together with environment and lifestyle.
Not all genetic disorders are inherited, and not all run obviously in families: some result from a brand-new mutation in the egg, sperm or embryo, while others, especially cancers, come from mutations a cell acquires during life. Calling a condition genetic describes its biological cause, not a person's worth, and most such conditions today can be understood, tested for, and in many cases managed.
Three conditions illustrate the range: cystic fibrosis (a single gene), Down syndrome (an extra chromosome), and most adult-onset diabetes (many genes plus environment), all genetic disorders in different senses.
Genetic disorder is an umbrella term spanning single genes, chromosomes and many-gene traits.
It helps to separate two questions: is a disorder genetic (caused by DNA changes) and is it inherited (passed from a parent). A new mutation makes a disorder genetic but not inherited.