A genetic mutation is a permanent alteration in the DNA sequence that makes up a gene. These changes can range from a single “letter” substitution to large-scale structural changes involving entire chromosomes. Mutations are broadly categorized by when and where they occur in the body’s cells. Understanding the difference between inherited and acquired mutations is fundamental to comprehending human health, disease risk, and genetic transmission.
Inherited Mutations: The Germline Legacy
Inherited mutations originate in the parental reproductive cells (egg or sperm) and are present at conception. Because the mutation is incorporated into the very first cell, it is subsequently present in virtually every cell of the resulting individual. This presence in the reproductive cells allows the mutation to be passed directly from parent to child, forming the basis for hereditary conditions that run in families. Once established, this type of mutation remains an unchanging part of the individual’s genetic code throughout life.
Acquired Mutations: Changes During a Lifetime
Acquired mutations, also known as somatic mutations, occur in any body cell after conception. These alterations accumulate throughout a person’s life and are not present in the egg or sperm. They arise either from errors that spontaneously occur during normal cell division or from damage caused by environmental exposures.
Environmental factors that induce acquired mutations include ultraviolet (UV) radiation and exposure to certain chemicals or toxins. Unlike inherited mutations, acquired changes are not uniformly distributed throughout the body; they are localized to specific tissues or cells. This patchy distribution creates a genetic pattern called mosaicism, where the body is composed of a mixture of cells, some with the mutation and some without. If the mutation occurs later in life, it may be confined to only a small group of cells, such as those within a specific organ.
Implications for Disease Risk and Transmission
The timing and location of a mutation fundamentally change its impact on disease risk and family transmission. Inherited mutations are associated with predictable risk and a clear pattern of family history. Since they are present in every cell, they can lead to congenital disorders or increase the lifetime risk for conditions like hereditary cancers.
For example, an individual who inherits a mutation in a gene like BRCA1 starts life with a genetic change that predisposes them to cancer. Testing for these mutations often involves a simple blood or saliva sample, and the results inform specialized cancer screening protocols for the individual and their relatives.
Acquired mutations are the driving force behind the vast majority of sporadic, non-hereditary diseases, particularly cancer. Most cancers develop when multiple acquired mutations accumulate over time in a single cell line, causing uncontrolled growth. Age is the biggest risk factor for acquired mutations because the longer a person lives, the more opportunity there is for DNA damage and copying errors to occur.
These somatic changes pose a risk only to the individual because the mutation is confined to non-reproductive body cells. Testing for acquired mutations is typically performed on a tissue sample, such as a tumor biopsy, to identify changes that may guide treatment decisions. Understanding whether a mutation is inherited or acquired is central to assessing personal health and family risk.