**This is a new page titled "De novo mutations" that I will be creating on Wikipedia, as a result nothing is underlined because all of the content is mine.**
De novo mutations
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A de novo mutation is any mutation that is found in an individual's genome, but is not present in their parent's genome.[1] Since the parents do not have this mutation, the child must have not inherited the mutation, and instead received it another way. Typically there are two ways for an individual to get a de novo mutation:
The first possibility involves receiving a de novo mutation via the parental germline (either mom's egg or dad's sperm).[2] People only express the DNA in their somatic cells, not their germline cells, so if there was a new mutation in the parent's germline cells they might not find out until they have a child. If there is a new mutation in the parent's germline, the mutation would be present in their children. The mutation would be considered de novo because the child would be the first person to carry the mutation in their somatic cells and show the phenotypic consequences of the mutation.
The second way an individual can get a de novo mutation that would show phenotypic consequences would be if a spontaneous mutation occurred in the zygote within the first few cell divisions.[2]
De novo mutations are often more deleterious than inherited mutations, as inherited mutations have gone through more stringent evolution.[1] Mutations that are inherited from parents tend to be less harmful because the mutations have been able to pass through generations in the family, therefore their phenotypic consequences were not deleterious. If an individual is carrying a de novo mutation, they are the first in the family to show the phenotypic consequences the mutation, leaving the mutation with the potential to be deleterious. If the mutation was extremely harmful, it would likely not be able to be passed on in the family because the individual carrying the mutation would not be able to produce viable offspring.
The severity of some de novo mutations allows for them to be good candidates for genetic diseases.[1] In fact, de novo mutations have been found to be associated with many genetic diseases that occur sporadically in families.[1]
De novo mutations via the parental germline
editOne way someone can acquire a de novo mutation is through a new mutation in the parental germline. A child could either receive this mutation from the mother's egg or father's sperm.[1] This mutation would not be expressed by the parent because the mutation is new and therefore not present in the parent's somatic cells, it is only present in their germline cells. Although the child is receiving a mutation from the parental germline, it is still considered de novo because the parent does not express or show the consequences of the mutation, only the child does.[1]
Every occurrence of DNA replication increases the chance of error in the copying of genetic information, potentially resulting in a mutation. If a mutation occurs during DNA replication in germline cells, that mutation would be passed onto the chid without being expressed by the parent.[1] Since sperm replicates actively and eggs do not, it is more common to receive a de novo germline mutation from the father.[1] In the case of females, there is a certain point where the eggs will stop replicating, yielding in a significantly lower chance of mutation.[1] However, in the case of males, the germline is always dividing and replicating, therefore the chance of a de novo mutation occurring in the male germline is much higher.[1]
De novo mutations that occur post-zygotically
editA post zygotic mutation that occurs in an individual is also considered a de novo mutation.[3] Such mutations can happen through errors in cell division, repair, or through an exogenous way (ie-UV light, smoking). After a cell becomes mutated, any daughter cell that divides from that original mutated cell will carry the same mutation.[3]
If a mutation occurs late in development then it will be harder to detect the mutation because the mutation will only be present in a select number of cells. Since the mutation would not be present in a lot of the cells, it makes it less likely that the person carrying this mutation would show phenotypic consequences. [3] However, if the mutation occurs within the first few stages of cell divisions in early in development, more cells would carry the mutation and it would be more likely that the individual would show the phenotypic consequences of the mutation because more cells would be affected. Mutations that occur early on in development may cause somatic mosaicism which refers to the occurrence of at least two genetically distinct populations of cells within the same individual.[4] The phenotypic consequences of somatic mosaicism are dependent on many factors including the developmental time at which the mutation occurs, the areas of the body that are affected, and the phenotypic effect of the mutation.[4]
References
edit- ^ a b c d e f g h i j Goriely, Anne (2016-08-01). "Decoding germline de novo point mutations". Nature Genetics. 48 (8): 823–824. doi:10.1038/ng.3629. ISSN 1061-4036.
- ^ a b Veltman, Joris A.; Brunner, Han G. (2012-07-18). "De novo mutations in human genetic disease". Nature Reviews. Genetics. 13 (8): 565–575. doi:10.1038/nrg3241. ISSN 1471-0064. PMID 22805709.
- ^ a b c Biesecker, Leslie G.; Spinner, Nancy B. (2013-05-01). "A genomic view of mosaicism and human disease". Nature Reviews. Genetics. 14 (5): 307–320. doi:10.1038/nrg3424. ISSN 1471-0064. PMID 23594909.
- ^ a b Lupski, James R. (2013-07-26). "Genome Mosaicism—One Human, Multiple Genomes". Science. 341 (6144): 358–359. doi:10.1126/science.1239503. ISSN 0036-8075. PMID 23888031.