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In contrast, discordance occurs when a similar trait is not shared by the persons. Studies of twins have shown that genetic traits of monozygotic twins are fully concordant, whereas in dizygotic twins, half of genetic traits are concordant, while the other half are discordant. Discordant rates that are higher than concordant rates express the ...
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).
The presence of a "T-sign" at the inter-twin membrane-placental junction is indicative of monochorionic-diamniotic twins (that is, the junction between the inter-twin membrane and the external rim forms a right angle), whereas dichorionic twins present with a "lambda (λ) sign" (that is, the chorion forms a wedge-shaped protrusion into the ...
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 ...
In the third pair found by Bouchard, the male twins were neither definitively concordant nor discordant, as both had relations with males and females, thus this pair may be concordant for bisexuality. Among the female twin pairs; four female twin pairs were all discordant, although the small number of cases prevent any strong conclusions. [30]
Sierra and her identical twin sister Sienna set the record for rarest type of discordant twinning and sharing the greatest height differential between living identical twins — and they're both ...
A 1952 study involving 33 pairs of identical twins found that 21% of them were discordant - that is, one of the twins had the ability and the other did not. [7] A 1971 study found that identical twins were 18% discordant, and 22% of non-identical twins were discordant, concluding that "hereditary factors strongly influences tongue rolling ...
However, when comparing the frequency of discordant pairs of handedness, pairs that exhibit opposite handwriting, there was little to no difference in frequency. The frequency of left-handedness in monozygotic dichorionic twins was 22% and the data of frequencies of left-handedness in monozygotic monochorionic twins was 23%. [2]