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Heteropaternal superfecundation is common in animals such as cats and dogs. Stray dogs can produce litters in which every puppy has a different sire. Though rare in humans, cases have been documented. In one study on humans, the frequency was 2.4% among dizygotic twins whose parents had been involved in paternity suits. [6]
In sectoral heterochromia, areas of the same iris contain two different colors, the contrasting colors being demarcated in a radial, or sectoral, manner. Sectoral heterochromia may affect one or both eyes. [31] It is unknown how rare sectoral heterochromia is in humans, but it is considered to be less common than complete heterochromia.
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]
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 ...
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: Getty Images/Unsplash (not the actual photo) Your chances of having twins have been growing a lot over the past few decades. According to a recent study from Oxford, around 1.6 ...
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.
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 ).