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Unique Types of Twins
Nature’s equivalent of “copy and paste”
Most twins fall into two main categories: identical or fraternal.
Identical twins are monozygotic, meaning that they originate from the same, single fertilized egg. In these cases, the egg eventually splits into two separate parts. But, since both twins still come from the same egg and sperm, they will have completely identical chromosomes.
On the other hand, fraternal twins are dizygotic, so their formation involves two distinct eggs that are released at the same time. Each egg will also be fertilized by a different sperm, so only about half of their chromosomes will be the same. As a result, while fraternal twins might have some shared characteristics, they will not be identical.
But beyond classifying twins as simply identical or fraternal, there are other types of twins that can also occur in unusual pregnancies.
Mirror image twins
Mirror image twins are similar to identical twins, except that they appear as mirror images of each other. The condition causes asymmetrical resemblances so that each twin’s features are opposite that of their sibling.
For example, some mirrored features can include birthmarks, freckles, or dimples on the opposite side of each twin. Mirror twins…
