There are two main categories of mutation based on the type of cell that the genetic change occurs in. These alterations to a person’s DNA can be inherited or acquired after fertilization. Here is a summary of the difference between hereditary and somatic DNA mutations.
* What Is a Mutation? *
A mutation is a permanent change to a cell’s DNA sequence. Deoxyribonucleic acid (DNA) is essentially the blueprint contained in every cell of an organism’s body. A mistake in the DNA may be very small, such as one wrong building block within the DNA molecule, or may be very large, affecting a substantial segment of a chromosome. Whatever the size, when mistakes occur in these molecular instructions, cells may not work properly.
There are two main categories of genetic mutation. Changes to a persons DNA can be inherited from a parent or can be acquired during that individual’s lifetime.
* Hereditary Germline Mutations *
Mutations are passed on from one generation to the next only if the DNA error occurs in germ cells also called gametes (sperm or eggs). These mutations which are passed from parent to child are called hereditary or germline mutations.
* De Novo and Somatic Mutations *
* New De Novo Mutations: Mutations that occur for the first time in one family member are termed new (de novo) mutations. All of the cells in your body originated one fertilized egg, which then divided, creating daughter cells that continued to divide. If one of the gametes that resulted in a fertilized egg had a genetic mutation, or if a mutation occurred shortly after fertilization, that genetic mistake would appear in the DNA of virtually every cell in the body.
* Somatic Mutations: If a mutation happens in somatic cells (the majority of the body’s cells that are not gametes), the mutation will be limited to the organism that it occurred in; not passed on to future generations. This type of genetic error is called an acquired or somatic mutation, and appears in the DNA of individual cells at some time during a person’s life. Acquired mutations can be caused by external, environmental factors such as ultraviolet radiation and other carcinogens, or can occur if a mistake is made during replication, when DNA copies itself to prepare for cell division (mitosis).
* Mutation Mosaicism *
Sometimes a mutation occurs in a single cell of a developing embryo. As all the cells of the developing fetus divide, those cells descended from the cell with the somatic mutation will carry the mutation while other cells will not. The individual will have some cells with the mutation and some cells without the genetic change. This condition is called mosaicism.
* Sources *
Genetic Mutation, National Library of Medicine NIH
Campbell, N. & Reece, J. (2005) Biology, Seventh Edition. Pearson, Benjamin Cummings.
