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A somatic mutation is a change in the DNA sequence of a somatic cell of a multicellular organism with dedicated reproductive cells; that is, ... for example, germ ...
Human somatic variations are somatic mutations (mutations that occur in somatic cells) both at early stages of development and in adult cells. These variations can lead either to pathogenic phenotypes or not, even if their function in healthy conditions is not completely clear yet.
The frequency of mutations in mouse somatic tissue (brain, liver, Sertoli cells) was compared to the mutation frequency in male germline cells at sequential stages of spermatogenesis. [3] The spontaneous mutation frequency was found to be significantly higher (5 to 10-fold) in the somatic cell types than in the male germline cells. [3]
With plants, some somatic mutations can be propagated without the need for seed production, for example, by grafting and stem cuttings. These type of mutation have led to new types of fruits, such as the "Delicious" apple and the "Washington" navel orange. [93]
In 1971, Knudson published the 2-hit hypothesis for mutation and cancer based on statistical analysis of inherited and sporadic cases of retinoblastoma. [21] He postulated that retinoblastoma developed as a consequence of two mutations; one of which could be inherited or somatic followed by a second somatic mutation.
The somatic mutation theory of ageing states that accumulation of mutations in somatic cells is the primary cause of aging. A comparison of somatic mutation rate across several mammal species found that the total number of accumulated mutations at the end of lifespan was roughly equal across a broad range of lifespans. [16]
The somatic mutations and epigenetic alterations caused by DNA damage and deficiencies in DNA repair accumulate in field defects. Field defects are normal-appearing tissues with multiple alterations (discussed in the section below), and are common precursors to development of the disordered and over-proliferating clone of tissue in a cancer.
The 16 possible mutation types of the substitution class C>A are shown as an example. Once the mutation catalog (e.g. counts for each of the 96 mutation types) of a tumor is obtained, there are two approaches to decipher the contributions of different mutational signatures to tumor genomic landscape: