Editing Somatic cell (section)

==Genetics and chromosomes==
Like all cells, somatic cells contain [[DNA]] arranged in [[chromosome]]s. If a somatic cell contains chromosomes arranged in pairs, it is called [[diploid]] and the organism is called a diploid organism. The gametes of diploid organisms contain only single unpaired chromosomes and are called [[haploid]]. Each pair of chromosomes comprises one chromosome inherited from the father and one inherited from the mother. In humans, somatic cells contain 46 [[chromosomes]] organized into 23 pairs. By contrast, gametes of diploid organisms contain only half as many chromosomes. In humans, this is 23 unpaired chromosomes. When two gametes (i.e. a spermatozoon and an ovum) meet during conception, they fuse together, creating a [[zygote]]. Due to the fusion of the two gametes, a human zygote contains 46 chromosomes (i.e. 23 pairs).{{cn|date=June 2024}}

A large number of [[species]] have the chromosomes in their somatic cells arranged in fours ("[[tetraploid]]") or even sixes ("[[hexaploid]]"). Thus, they can have diploid or even triploid germline cells. An example of this is the modern cultivated species of [[wheat]], ''Triticum aestivum L.'', a hexaploid species whose somatic cells contain six copies of every [[chromatid]].{{cn|date=June 2024}}

The frequency of spontaneous [[mutation]]s is significantly lower in advanced male [[germ cell]]s than in somatic cell types from the same individual.<ref name="pmid9707592">{{Cite journal |vauthors=Walter CA, Intano GW, McCarrey JR, McMahan CA, Walter RB |date=August 1998 |title=Mutation frequency declines during spermatogenesis in young mice but increases in old mice |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=95 |issue=17 |pages=10015–10019 |bibcode=1998PNAS...9510015W |doi=10.1073/pnas.95.17.10015 |pmc=21453 |pmid=9707592 |doi-access=free}}</ref> Female germ cells also show a mutation frequency that is lower than that in corresponding somatic cells and similar to that in male germ cells.<ref name="pmid23153565">{{Cite journal |vauthors=Murphey P, McLean DJ, McMahan CA, Walter CA, McCarrey JR |date=January 2013 |title=Enhanced genetic integrity in mouse germ cells |journal=Biology of Reproduction |volume=88 |issue=1 |pages=6 |doi=10.1095/biolreprod.112.103481 |pmc=4434944 |pmid=23153565}}</ref> These findings appear to reflect employment of more effective mechanisms to limit the initial occurrence of spontaneous mutations in germ cells than in somatic cells. Such mechanisms likely include elevated levels of [[DNA repair]] enzymes that ameliorate most potentially mutagenic [[DNA damage (naturally occurring)|DNA damages]].<ref name="pmid23153565" />