Difference Between Germline and Somatic Mutation

Main Difference – Germline vs Somatic Mutation

Germline and somatic mutations are the two types of mutations that occur in the body cells of multicellular organisms in different stages of life. A mutation is a permanent change in the nucleotide sequence of the organism’s genome. Errors during DNA replication or DNA damages may cause the alterations of the nucleotide sequence. However, some changes in the nucleotide sequence of genes may not affect the amino acid sequence of the protein. Thus, their phenotype of the offspring is also not affected. Nevertheless, a single nucleotide change in the sequence of the gene could have an enormous effect on the phenotype of the offspring. As said before, Germline and somatic mutations are the two types of mutations. Germline mutations occur in different stages of cells in the process of gametogenesis. Somatic mutations occur in regular body cells such as liver cells, muscle cells, and skin cells. The main difference between germline and somatic mutation is that germline mutations are inheritable whereas somatic mutations cannot be inherited by the offspring.

Key Areas Covered

1. What is a Germline Mutation
      – Definition, Features, Significance
2. What is a Somatic Mutation
      – Definition, Features, Significance
3. What are the Similarities Between Germline Mutation and Somatic Mutation
      – Outline of Common Features
4. What is the Difference Between Germline and Somatic Mutation
      – Comparison of Key Differences

Key Terms: Acquired Mutation, Germ Cell, Germline Mutations, Hereditary Mutations, Multicellular Organisms, Offspring, Somatic Clone, Somatic Mutations

What is a Germline Mutation

A germline mutation is a heritable change in the DNA of a germ cell. A germ cell is designated to become either an egg cell or a sperm cell. Germline mutations can also occur in the zygote when it is in the single-celled stage. Germline mutations are inherited by the offspring since they are a change in the DNA sequence of sex cells. Therefore, these type of mutations can be found in every cell of the offspring. On that account, germline mutations are also referred to as hereditary mutations. Since germline mutation can be found in every cell of the organism’s body, the mutation becomes a constitutional mutation in the offspring.

Figure 1: Inheritance of tumor retinoblastoma

Oxidative DNA damages are the most common reason for germline mutations. 20% of the genetic disorders in the offspring are caused due to germline mutations. Germline mutations may also cause cancers in the offspring such as tumor retinoblastoma of the eye and the Wilms tumor in kidneys. The frequency of the occurrence of germline mutations is lower than that of somatic mutations. The inheritance of tumor retinoblastoma is shown in figure 1. 

What is a Somatic Mutation

A somatic mutation is an acquired mutation, which occurs in a single body cell of an individual after its conception. Somatic mutations pass only to the descending cells of the mutated cell. Hence, only a sector of the mutated individual bears the somatic mutation. Thus, somatic mutations produce individuals with somatic mosaicism, containing cells with different genotypes within the same individual.

Most frequently, somatic mutations are caused by environmental factors such as the exposure to certain chemicals and UV radiation. Since somatic mutations occur in body cells rather than sex cells, these type of mutations are not inheritable to the offspring. However, in plants, somatic mutations can be inherited through asexual reproduction. The new generation with the somatic mutation is called as the somatic clone. Red delicious apples and navel oranges are such somatic clones. The somatic mutations in animals can be inherited by cloning of cells which contain the mutation. Mutations in the proto-oncogenes can generate cancer tumors. Tumors occur due to the uncontrolled division of somatic cells in the body.

Figure 2: Garden moss rose

The somatic mutations in garden moss rose produce flowers in different colors, which can pass to a new generation through asexual reproduction. Typically, orange color moss rose is considered as a mutant type. Different flower colors of garden moss rose are shown in figure 2.

Similarities Between Germline and Somatic Mutations

• Germline mutations and somatic mutations are the two types of mutations that occur in animals and plants.
• Germline mutations and some somatic mutations are inheritable.

Difference Between Germline and Somatic Mutations

Definition

Germline Mutations: A germline mutation is any detectable and heritable change in the germ cell lineage.

Somatic Mutations: A somatic mutation is any mutation in a somatic tissue of an organism, which results in a genetically mosaic individual.

Known as

Germline Mutations: Germline mutations are also known as hereditary mutations.

Somatic Mutations: Somatic mutations are also known as acquired mutations.

Occur in

Germline Mutations: Germline mutations occur in the different cell stages that appear during the gametogenesis.

Somatic Mutations: Somatic mutations occur in the regular body cells such as liver, muscle, and skin cells.

Period

Germline Mutations: Germline mutations occur during gametogenesis.

Somatic Mutations: Somatic mutations can occur at any time of the organism’s life.

Found in

Germline Mutations: Germline mutations are found in all body cells of the new organism.

Somatic Mutations: Somatic mutation can be found in a part of the body or tissue.

Inheritance

Germline Mutations: Germline mutations are inheritable to the offspring.

Somatic Mutations: Somatic mutations cannot be inherited to the offspring.

Influence

Germline Mutations: Germline mutations affect each and every cell in the body of the new organism.

Somatic Mutations: The influence of the somatic mutations is local. It typically affects a single tissue.

Evolution

Germline Mutations: Germline mutations have an effect on the evolution through natural selection.

Somatic Mutations: Somatic mutations have no effect on the evolution.

Role in Cancers

Germline Mutations: Tumor retinoblastoma of the eye and the Wilms tumor in kidneys are two types of cancers produced by germline mutations.

Somatic Mutations: Mutated proto-oncogenes produce cancer tumors in the body.

Conclusion

Germline mutations and somatic mutations are two types of mutations that can occur in plants and animals. Germline mutations can occur in different stages of cells, starting from germ cells to sex cells. Since germline mutations occur in sex cells, they are inheritable, and whole body cells of the new organism contain the mutation. Somatic mutations can occur in body cells due to the exposure to external environmental factors. Unless cloned, somatic mutations are not inherited. Thus, the main difference between germline and somatic mutation is their ability to inherit.

Reference:

1. “Medical Definition of Germline mutation.” MedicineNet. N.p., n.d. Web. Available here. 18 July 2017. 
2. “Somatic mutation.” Encyclopædia Britannica. Encyclopædia Britannica, inc., n.d. Web. Available here. 18 July 2017.

Image Courtesy:

1.”Inheritance of a germline loss-of-function mutation in a TSG dramatically increases the risk of cancer” By WassermanLab – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “Portulaca grandiflora mutant1” By JerryFriedman – Own work (CC BY-SA 3.0) via Commons Wikimedia