After reading the article, I was curious to find more information about the twins, since I wasn’t satisfied with the info provided. On the internet I found a kind of essay about twins. To be precise, about “What makes twins biologically and psychologically alike and what are the causes of any differences in a pair of twins?” I’ll sum it up briefly and if you want to read it yourself, follow the link:
http://serendip.brynmawr.edu/biology/b103/f00/web3/hayesconroya3.html
There are several types of twins:
- fraternal or dizygotic twins – if there are two eggs released and both fertilized. The twins can than be male-male, female-female or female-male
- identical or monozygotic – when a fertilized egg splits. The twins can then be either female-female or male-male. What struck me as fascinating is the phenomenon of so called
mirror imaging. If the morula (the fertilized egg) splits between day 10-13, the twins can be mirror images of each other. One can be left-handed while the other right-handed or they can even have birthmarks on the same part of the body, the one on the left and the other on the right.
Siamese twins (named after famous twins from Siam – joined at the breastbone) are also monozygotic and are the result of the “too late” splitting up (after day 13), which is why the division is not successful. - other types.
Aren’t all these “phenomena” fascinating? I wanted to find more info about twins on a genetic level (from morula to fetus, from fetus to I don’t know what), but unfortunately I ran out of time. Maybe some other time. I’ll be back!!
I’ve found it! The theory of semi-identical twins:
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