"semi-identical" twins (sesquizygotic)

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In summary, a set of semi-identical twins was born in Queensland, Australia, which was not supposed to happen. These twins share 100% of their maternal DNA, but only 78% of their paternal DNA, suggesting that the fertilized egg received DNA from two separate sperm cells. This phenomenon can also be seen as a chimera, where one egg contains two sets of male DNA. This goes against the traditional understanding of genetics and highlights the importance of sample size and detection methods in scientific discoveries.
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jim mcnamara
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A set of twins was born in Queensland Australia that is almost identical. This was not supposed to happen.
Identical twins arise from a single fertilized egg, derived from fertilization by a single sperm cell, that divides into two separate but genetically identical fertilized eggs. After this the two cells go their merry way on toward creating two genetically identical babies. In the Queensland case, the children share 100% of maternal DNA (as expected), but only 78% of paternal DNA. This means that the fertilized egg most likely got its DNA from two separate sperm cells.

https://medicalxpress.com/news/2019-02-semi-identical-twins-pregnancy.html

This may also be thought of as a kind of chimera: one egg, two sets of male DNA:
https://en.wikipedia.org/wiki/Chimera_(genetics)
 
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jim mcnamara said:
This was not supposed to happen.

In my experience with biology, and particularly genetics and development, human inclinations towards clear categories are constantly smashed apart.
 
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I think it is more of a matter of sample size and detection. If you observe something 100K times with the same result, using constant methods, people tend to ossify the concept.

Then new technology comes along expanding the available sample size as well as providing previously unavailable methods, voila! something new shows up. Blood types are good example. At the other end of the spectrum might be exosomes. Not detected and reported until ~2012.
 

1. What are semi-identical twins (sesquizygotic)?

Semi-identical twins, also known as sesquizygotic twins, are a rare type of twins that share a mix of identical and fraternal characteristics. They are created when a single egg is fertilized by two different sperm, resulting in three sets of chromosomes instead of the usual two.

2. How are semi-identical twins different from identical and fraternal twins?

Semi-identical twins share 75% of their genetic material, while identical twins share 100% and fraternal twins share 50%. This means that semi-identical twins are more genetically similar than fraternal twins, but not as identical as identical twins.

3. How common are semi-identical twins?

Semi-identical twins are extremely rare, with only two reported cases in the world so far. This makes them even rarer than identical twins, which occur in about 3-4 per 1000 births.

4. Can semi-identical twins be different genders?

Yes, semi-identical twins can be different genders, just like fraternal twins. This is because they are formed from two different sperm, one carrying a Y chromosome and the other carrying an X chromosome.

5. What are the potential health implications for semi-identical twins?

Since semi-identical twins have an unusual genetic makeup, there is a possibility that they may have health issues related to their unique chromosome arrangement. However, more research is needed to fully understand the potential health implications for semi-identical twins.

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