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Heterochromia is a variation in coloration most often used to describe color differences of the iris, but can also be applied to color variation of hair [1] or skin. Heterochromia is determined by the production, delivery, and concentration of melanin (a pigment). It may be inherited, or caused by genetic mosaicism, chimerism, disease, or ...
On January 22, 2019, the National Society of Genetic Counselors released an article Chimerism Explained: How One Person Can Unknowingly Have Two Sets of DNA, where they state, "where a twin pregnancy evolves into one child, is currently believed to be one of the rarer forms. However, we know that 20 to 30% of singleton pregnancies were ...
A human chimera is a human with a subset of cells with a distinct genotype than other cells, that is, having genetic chimerism.In contrast, an individual where each cell contains genetic material from a human and an animal is called a human–animal hybrid, while an organism that contains a mixture of human and non-human cells would be a human-animal chimera.
Twins are concordant when both have or both lack a given trait. [ 1 ] The ideal example of concordance is that of identical twins , because the genome is the same, an equivalence that helps in discovering causation via deconfounding , regarding genetic effects versus epigenetic and environmental effects ( nature versus nurture ).
Occasionally, heterochromia can be a sign of a serious medical condition. A common cause in females with heterochromia is X-inactivation, which can result in a number of heterochromatic traits, such as calico cats. Trauma and certain medications, such as some prostaglandin analogues, can also cause increased pigmentation in one eye. [88]
Image credits: anothermegan #3. Me and my twin are complete opposites. I have a pixie cut and she has long hair. I am a musician and she is a mathematician. I am gay and she is straight.
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 ...
If the parents are both right-handed, in dizygotic and monozygotic twins there is a 21% chance of one being left-handed. If one parent is left-handed, in DZ and MZ twins there is a 57% chance of one being left-handed. If both parents are left-handed, it is almost certain one twin will be left-handed. [citation needed]