The human body is made up of two basic types of cells called germ cells and somatic cells. Among them germ cells are the sex cells(egg and sperm) that are responsible for reproduction and give rise to offspring, all the other cell except germ cells are called somatic cells and the mutations in these cells are called somatic mutation.
There is a term called Chimerism in which the occurrence of a somatic mutation in the early stages of embryonic development or during fusion of the zygotes, it leads to an organism possessing more than one DNA.
In somatic mutation the organism acquires the mutation after the conception, they are called somatic because they occur in the somatic cells of the body like skin cells. They cannot be passed to future generation because they do not form gametes, unlike germ cells, so they are not inherited from the parents. The risk of somatic mutation is also high due to some environmental factors like exposure to UV, viral and bacterial infection, ingestion of toxic material, unhealthy life.
As the mutation of somatic cells changes the genetic makeup of the cells, if that cell reproduces than it will transfer mutation to progeny cells also, and if the mutation occurs at early developmental stages it can lead to a condition in which the organism can have two sets of DNA in the body.
Detection of somatic mutation –
The most common method of detecting somatic mutation is by taking a sample of DNA of the mutated cell as well as the sample of a normal cell, both the samples than purified and their DNA is sequenced. By obtaining the sequences they are compared and matched to identify variation and deviation and to identify mutated sites.
Another way of detection is by probing, in this both samples of DNA are taken and then they are probed with various DNA markers and the result obtained is analyzed.
Diseases caused by somatic mutations –
Somatic mutations give rise to a variety of genetic disorders like Chimerism. The presence of a mutation in the somatic genes interrupts the sequencing and functions of the gene and the cells. The most common disease caused by somatic mutation is cancer, there are some other diseases caused by somatic mutation listed below-
- Baraitser- winter syndrome
- Borching- Opitz syndrome
- Incontinentia pigment
- Kabuki syndrome
- Klippel- trenaunay syndrome
- Maffucci syndrome
- Paroxysmal nocturnal hemoglobinuria
- Proteus syndrome
- Schinzel- Giedion syndrome
Example of somatic mutation –
A common example of somatic mutation can be seen in the dogs, variation of the color of the fur coat. When there is breeding in the dogs between same species then the puppy will have the color from one of the parent, but if there is somatic mutation then the there may be the inheritance of color of coat from both the parents.
For example, if a black German shepherd is mated with yellow German shepherd then the puppy may have the brown or yellow color but in the case of somatic mutation, there may be both colors present in the puppy.