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Name: cwarrin
Status: N/A
Age: N/A
Location: N/A
Country: N/A
Date: Around 1993


Question:
How are Siamese twins formed, and what is the chances of having them?



Replies:
Siamese twins are formed when monozygotic twins (arising from a ingle fertilized egg) fail to completely separate from each other during the process of cell division. In a "regular" pregnancy, a single fertilized egg will undergo cellular division, the cells eventually differentiating into distinct organs and tissues. In the case of identical twins, however, a set of circumstances which are not entirely understood causes a separation of cells early in the division process, before actual differentiation begins, and the two halves then go on to form complete fetuses. Siamese twins, however, separate late in the division process, perhaps even after differentiation of cells has begun, and thus form into two fetuses with certain tissues or cell masses shared between them, due to their failure to separate completely before then.

Wordsworth



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