Somatic mutation

This distinction is blurred in plants, which lack a dedicated germline, and in those animals that can reproduce asexually through mechanisms such as budding, as in members of the cnidarian genus Hydra.

For example, in mammals, somatic cells make up the internal organs, skin, bones, blood, and connective tissue.

Once this segregation has occurred in the embryo, any mutation outside of the germline cells can not be passed down to an organism's offspring.

[2] Somatic mutations that occur later in an organism's life can be hard to detect, as they may affect only a single cell—for instance, a post-mitotic neuron;[3][4] improvements in single cell sequencing are therefore an important tool for the study of somatic mutation.

Plants and basal animals such as sponges and corals instead generate gametes from pluripotent stem cells in adult somatic tissues.

[9] Somatic mutations can also be passed down to offspring in organisms that can reproduce asexually, without production of gametes.

[10] A mutation present in the tissue that gives rise to the daughter organism would be passed down to that offspring.

As with germline mutations, mutations in somatic cells may arise due to endogenous factors, including errors during DNA replication and repair, and exposure to reactive oxygen species produced by normal cellular processes.

Mutagens can be physical, such as radiation from UV rays and X-rays, or chemical—molecules that interact directly with DNA—such as metabolites of benzo[a]pyrene, a potent carcinogen found in tobacco smoke.

They measured the rate of single nucleotide variants (SNVs), most of which are a consequence of replication error.

The mutation rate in antigen-binding coding sequences of the immunoglobulin genes is up to 1,000,000 times higher than in cell lines outside the lymphoid system.