PMC:1852721 / 42051-43776 JSONTXT

{"project":"2_test","denotations":[{"id":"17357067-14210613-2054055","span":{"begin":1212,"end":1214},"obj":"14210613"},{"id":"17357067-14732866-2054056","span":{"begin":1715,"end":1717},"obj":"14732866"},{"id":"17357067-15164071-2054057","span":{"begin":1719,"end":1721},"obj":"15164071"},{"id":"17357067-12042769-2054058","span":{"begin":1723,"end":1725},"obj":"12042769"}],"text":"Extensions on Mendelism in MIM/OMIM\nClassically, the determinants of variation are divided into genetic and environmental (a.k.a. exogenous or nongenetic). Random variation, “chance,” is also an important determinant. A useful demonstration of both genetics and chance (stochastic variation) in determination of a particular phenotype is provided by dermatoglyphic patterns (MIM %125590): presumably, “fingerprints” are different in every human being, even identical twins. The basic differences are laid down by the DNA of the individual; additional differentiation is provided by stochastic differences in the embryologic development of the finger pads, even in individuals with a shared genome, identical twins. (For a discussion of the difference between DNA fingerprint and dermatoglyphic fingerprints and an illustrative comparison of the two types in a pair of MZ twins, see the report of the National Research Council on DNA technology in forensic science.39)\nAccording to the role of genetic factors in pathogenesis, I and others found it useful in the early stages of the development of medical genetics to divide disease, rather arbitrarily to be sure, into Mendelian, chromosomal, and multifactorial.40 The arbitrary nature of this classification does not detract from its usefulness; all classifications are to some extent artificial. Consistent with the Garrodian perspective, all genetic variation, including that with only a contributing role in the multifactorial basis of a complex trait and perhaps even some chromosomal (genomic) variation, should be cataloged in OMIM.\nIn the past 20 years, epigenetic variation has become evident as a fourth major etiopathogenetic class, especially in cancer.41, 42, 43"}