Hereditary and Somatic DNA Mutations

Germ-line De Novo and Acquired Mistakes in the Genetic Instructions

May 1, 2008 Tami Port

There are two main categories of genetic mutation based on the type of cell they occur in. Changes to a person's DNA can be inherited or acquired after fertilization.

A mutation is a permanent alteration of 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 or Somatic Mutations

New De Novo Mutations

Mutations that occur only in gametes or that occur just after fertilization, 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 that mutation would appear in as a mistake 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 during 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.

More Information on DNA & Genetics

For additional resources on genetics and cell biology, see the science website Science Prof Online.

Sources

Genetic Mutation, National Library of Medicine NIH

Campbell, N. & Reece, J. (2005) Biology, Seventh Edition. Pearson, Benjamin Cummings.

The copyright of the article Hereditary and Somatic DNA Mutations in Genetics & Evolution is owned by Tami Port. Permission to republish Hereditary and Somatic DNA Mutations in print or online must be granted by the author in writing.

Mutations and Stage of an Organism's Development

What do you think about this article?

---

NOTE: Because you are not a Suite101 member, your comment will be moderated before it is viewable.

post your comment

What is 2+3?