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The human twin birth rate in the United States rose 76% from 1980 through 2009, from 9.4 to 16.7 twin sets (18.8 to 33.3 twins) per 1,000 births. [5] The Yoruba people have the highest rate of twinning in the world, at 45–50 twin sets (90–100 twins) per 1,000 live births, [6] [7] [8] possibly because of high consumption of a specific type of yam containing a natural phytoestrogen which may ...
The word zygosity may also be used to describe the genetic similarity or dissimilarity of twins. [6] Identical twins are monozygotic, meaning that they develop from one zygote that splits and forms two embryos. Fraternal twins are dizygotic because they develop from two separate oocytes (egg cells) that are fertilized by two separate sperm.
No two humans are genetically identical. Even monozygotic twins (who develop from one zygote) have infrequent genetic differences due to mutations occurring during development and gene copy-number variation. [1] Differences between individuals, even closely related individuals, are the key to techniques such as genetic fingerprinting.
The discovery of DNA as the blueprint for life and breakthroughs in molecular genetics research came from the combined works of many scientists. In 1869, chemist Johann Friedrich Miescher, who was researching the composition of white blood cells, discovered and isolated a new molecule that he named nuclein from the cell nucleus, which would ultimately be the first discovery of the molecule DNA ...
The power of twin designs arises from the fact that twins may be either identical (monozygotic (MZ), i.e. developing from a single fertilized egg and therefore sharing all of their polymorphic alleles) or fraternal (dizygotic (DZ), i.e. developing from two fertilized eggs and therefore sharing on average 50% of their alleles, the same level of genetic similarity found in non-twin siblings).
Unless the twins live eerily similar lives, those bonds will snap at different temperature points and quickly identify who's who. Police can spot differences between identical twins by melting DNA ...
The missing part is the mapping between the genotype and phenotype space. This leads to a "sleight of hand" (as Lewontin terms it) whereby variables in the equations of one domain, are considered parameters or constants , where, in a full-treatment, they would be transformed themselves by the evolutionary process and are functions of the state ...
Fraternal or dizygotic (DZ) twins on average share half their genes (assuming there is no assortative mating for the trait), and so identical or monozygotic (MZ) twins on average are twice as genetically similar as DZ twins.